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I've got my tune dialed in pretty good now, but I found breakups when my AFR was richer than 11:1 under boost. Some guys think it's due to my plug gap being wide (.044), although it should make more power leaner than 11:5 anyway so that's where I'm dialed in now. I may close the gap a little bit, but I've always been told run the widest gap you can for the AFR you want to run.
Biggest 'issue' I have now is I'm just not seeing as much boost as I'd expect from the impeller speed. I'm going to hook up a second map sensor before my IC to determine if that's causing a lot of pressure drop. If not, and if the 6.8l engine is just too consuming for the t-trim, I'll probably just ramp the timing back out to where it would be naturally aspirated.
If anyone cares, the numbers are:
RPM 5800 (cam doesn't make power past that - nx276hr12)
Impeller speed 47,000
Boost 5.1ish PSI
Ambient temp 68*
IAT temp 91* in boost
Outlet temp of blower 220+ degrees
Timing 22*
The max efficient impeller speed on this blower is around 45,000 so putting a smaller blower pulley to make more boost doesn't make much sense. No apparent boost leaks, so I suspect the cheap air-to-air IC is restrictive or the blower is too small for the motor.
SO I'm going to add a second MAP for recording. I know there is some pressure loss due to density changes with the IC, which I think you can calculate based on in/out temperature, but if the pressure drop is significant I might switch to the air/water IC I have on the shelf.
If pressure drop isn't a huge deal, I'll probably just ramp the timing in, maybe 28 degrees or so.
Lol i dont run wider than .035 in na applications
22 deg seems low
more timing maY help. I’d just go tighter gap
Just going by what Ford does on this ignition system (EDIS). But yeah, I think I was getting spark blowout when my fuel was way rich. Car pulls hard now at 11.5:1. Probably reduce the gap on the next plug change.
But, only 5 psi is sad.. I know I need to determine if it's pressure drop, or just too small of a blower. If it's the later, I'm thinking just ramp the timing back out as if it were n/a. Figure 5psi intercooled doesn't really require much if any spark retard?
It is what it is. Few psi isnt much if your na motor isnt on the ragged edge on the fuel you are using and the heads arent super fast burning. 11:1 pump gas motor with few psi, sure i would be yanking alot more timing. 9.5-10:1? Much better
2-3 deg out at 5 psi i feel is safe for that on pump gas well intercooled. Stock iron head deal i might be out 4-5. My 305 i was out maybe even more as i was looking at the factory knock sensor and it didnt seem happy but then again it was tripping when it was naturally aspirated on 93 oct lol so im sure it was false. But i was working that tune slowly and safely while battling apparent ignition and or valve float issues so never did find what was best
I remember the old rule of thumb was one degree for every pound of boost, so without actually seeing Joe's SA table, we're kind of in the dark. I'm not even sure if he meant 22* before or 22* after the 5-psi of boost pressure, hoping he meant after. But yeah, his compression is what made me say that in my other post. He's probably making more heat in that engine at 5-psi than I am at 15-psi, and my timing is at 15*...
on race motor on race gas or even e85 the trend now is nothing til 5-10 psi depending on the combo then around half deg per pound after. Roughly.
if you built a motor for 20+ psi to live, then yeah 5 isnt alot of boost so dont pull anything. If its a 11:1 street car that you want to add some boost to, might want to keep it abit safer than half deg per lb lol. 1 per lb is not a bad idea
stock bottom end lsx stuff also may want to keep timing out for head sealing issues on bottom end longevity
I remember the old rule of thumb was one degree for every pound of boost, so without actually seeing Joe's SA table, we're kind of in the dark. I'm not even sure if he meant 22* before or 22* after the 5-psi of boost pressure, hoping he meant after. But yeah, his compression is what made me say that in my other post. He's probably making more heat in that engine at 5-psi than I am at 15-psi, and my timing is at 15*...
- Rob
At 3,000 RPM its 32* under 100kpa, and 22* above. Years ago (like 20) I used to do the whole retarding under boost hing, but then Bruce Plecan told me to watch what happens to EGT when you do that, and I was amazed at the EGT spike. So Now I just lock in whatever my boost timing will be rather than retarding under boost.
The motor is 9.3:1, with a nx276 cam, was set up for boost. Not a on the edge street motor.
AFR 210 heads, and they typically don't recommend as aggressive advance as an older iron head chamber.
93 octane. It's eating a lot of fuel so I know it's making power, I just am thinking maybe the blower is smaller than I thought it would be so maybe ramp out the advance.
So soon as it sees boost or 101+ kpa it goes straight to 22 deg?
i feel like that is taking away to much power instantly in the 101-120 kpa range as it goes to 5 psi or i assume 135 kpa. For a turbo car the egt spike can be desirable for spool. I would think dropping from 32 to 22 instant would spike egt hard. I do this to help spool my car but a blower dont need it
I agree with Justin, that is a significant drop in timing once you're over 100-kPa. I pieced this base together when I first slapped on the 3-Bar MAP sensor, but I smoothed it out since then. My total at 100-kPa n/a is 35*. I start to see 1-psi at 2500-RPM...
At 3,000 RPM its 32* under 100kpa, and 22* above. Years ago (like 20) I used to do the whole retarding under boost hing, but then Bruce Plecan told me to watch what happens to EGT when you do that, and I was amazed at the EGT spike. So Now I just lock in whatever my boost timing will be rather than retarding under boost.
Can't comment on Bruce because a lot has changed since he passed, and he was a Turbo Buick guy, and their science is always changing with those guys. He might have felt differently today. But anyways, we've been through this years ago, and arguments always seem to ensue, but lets keep discussing. In my opinion, just like years ago, your engine is just too efficient, and that is to your credit. T-Trim's support up to what, 825 FWHP pulley'd up?
Your engine is already making, lets say for arguments sake, 500-FWHP, yes? Difference being 65% from your base horsepower to what the T-Trim maxes out at. So at 5-psi you're making 35% more horsepower, call it at 675-FWHP,. Your impeller speed is at 47,000, with the max impeller speed for the T-Trim being 55,000. Bottom line is the blower is just too small for your engine. Step up to a Y-Trim, or just go back to the turbo and be done with it...
So soon as it sees boost or 101+ kpa it goes straight to 22 deg?
i feel like that is taking away to much power instantly in the 101-120 kpa range as it goes to 5 psi or i assume 135 kpa. For a turbo car the egt spike can be desirable for spool. I would think dropping from 32 to 22 instant would spike egt hard. I do this to help spool my car but a blower dont need it
My 100kpa row is 32*, my 110kpa row is 22*, so it should interpolate between 32 and 22 for the first 1.5 psi or so.
Max I've seen is 138kpa.
I could probably do something like keep it at 32 until 120kpa, then maybe 30, 28..
My VE table is set up for 100, 130, 160, 190 although I could re-scale it as needed but I don't suspect I need much resolution in boost.
Factory 400 block? What rpm does it hit peak boost? May not want all that timing back in it on stock block but it could take few more degrees in a ramp less than what you have now. 32 at 100. 28 at 120. 25 at 138. That could be fun.
Can't comment on Bruce because a lot has changed since he passed, and he was a Turbo Buick guy, and their science is always changing with those guys. He might have felt differently today. But anyways, we've been through this years ago, and arguments always seem to ensue, but lets keep discussing. In my opinion, just like years ago, your engine is just too efficient, and that is to your credit. T-Trim's support up to what, 825 FWHP pulley'd up?
Your engine is already making, lets say for arguments sake, 500-FWHP, yes? Difference being 65% from your base horsepower to what the T-Trim maxes out at. So at 5-psi you're making 35% more horsepower, call it at 675-FWHP,. Your impeller speed is at 47,000, with the max impeller speed for the T-Trim being 55,000. Bottom line is the blower is just too small for your engine. Step up to a Y-Trim, or just go back to the turbo and be done with it...
- Rob
No argument to anything you said above. But.. I'm not trying to make more power, really. Just surprised it's only showing 5psi at the intake manifold.
Factory 400 block? What rpm does it hit peak boost? May not want all that timing back in it on stock block but it could take few more degrees in a ramp less than what you have now. 32 at 100. 28 at 120. 25 at 138. That could be fun.
Factory 2 bolt 400. Forged crank, sir rods, forged pistons. 9.3:1, afr210 heads, nx276hr cam.. Cam is done by 5800-5900. I'm seeing abour 138kpa right around there. I've spun it to 6k, but it didn't make more power or boost. The shift light just stays on longer lol.
the lt1 ysi car i help with is fairly similar and honestly it too has been a bit lower on boost than i would have thought. we are at 58k with cog drive at 7k and have been seeing 12-13#.
388", roughly 9.5 compression, cnc trickflow 212cc heads, mid 240's duration solid roller.
I believe you have a supercharger that isn't very efficient on bigger motors coupled with an innercooler that isn't very efficient. As you are near sea level and were on a 68* F day, I'm going to assume you are near a standard day to make my math a little easier/ less error prone. A decently headed 412 should produce near 480 Horsepower Gross at the flywheel N/A (about 1.17 Horsepower per cubic inch at your 5800 RPM) . using the provided intake manifold pressure, your pressure ratio is around 1.34. As your intake manifold air temps weren't to high at 91*F, its safe to assume the engine was making around 600 Gross horsepower at 5.1 PSI. With Gross Horsepower numbers, we can assume the engine is consuming 10 Lb of air per minute per 100 Gross Horsepower, thus it's consuming approximately 60 Lb of air per minute.
According to the compressor map for Vortech, the V1-T Trim supercharger produces 60 Lb/Min, and the known blower speed is 47,000 RPM, out of the upper efficiency range of the supercharger. The downfall of spinning the blower outside of its efficiency range/ low efficiency (Thus the 220+ Degree Fahrenheit discharge temps) is crippling an innercooler that might not be the best fit. This is further backed up with Innercooler efficiency at {(220-91)/ (220-68)} 84.86%. With such a high temp out of the blower, it signals that the blower is really out of the efficiency wheelhouse, and with a delta of 23* F between the discharge tube of the innercooler and ambient temperature, the innercooler can't dissipate anymore heat efficiently.
Once we have the air pressure going into the innercooler, we can calculate the pressure drop across the innercooler. This would give us a better picture at how restrictive the innercooler truly is. However, blower temp will rise even more with higher ambient temperatures, thus causing a decrease in innercooler efficiency. This will only exaggerate the issue of lower intake boost. The best advice, step up to a larger supercharger. maybe a V7-Ysi
I believe you have a supercharger that isn't very efficient on bigger motors coupled with an innercooler that isn't very efficient. As you are near sea level and were on a 68* F day, I'm going to assume you are near a standard day to make my math a little easier/ less error prone. A decently headed 412 should produce near 480 Horsepower Gross at the flywheel N/A (about 1.17 Horsepower per cubic inch at your 5800 RPM) . using the provided intake manifold pressure, your pressure ratio is around 1.34. As your intake manifold air temps weren't to high at 91*F, its safe to assume the engine was making around 600 Gross horsepower at 5.1 PSI. With Gross Horsepower numbers, we can assume the engine is consuming 10 Lb of air per minute per 100 Gross Horsepower, thus it's consuming approximately 60 Lb of air per minute.
According to the compressor map for Vortech, the V1-T Trim supercharger produces 60 Lb/Min, and the known blower speed is 47,000 RPM, out of the upper efficiency range of the supercharger. The downfall of spinning the blower outside of its efficiency range/ low efficiency (Thus the 220+ Degree Fahrenheit discharge temps) is crippling an innercooler that might not be the best fit. This is further backed up with Innercooler efficiency at {(220-91)/ (220-68)} 84.86%. With such a high temp out of the blower, it signals that the blower is really out of the efficiency wheelhouse, and with a delta of 23* F between the discharge tube of the innercooler and ambient temperature, the innercooler can't dissipate anymore heat efficiently.
Once we have the air pressure going into the innercooler, we can calculate the pressure drop across the innercooler. This would give us a better picture at how restrictive the innercooler truly is. However, blower temp will rise even more with higher ambient temperatures, thus causing a decrease in innercooler efficiency. This will only exaggerate the issue of lower intake boost. The best advice, step up to a larger supercharger. maybe a V7-Ysi
I'm struggling with reading that map, but I thought if you follow the impeller speed, 45,000 = 80lb / min ?
The '70% efficiency' island looks like 45k or so would be in the island if the pressure ratio was around 2.0,
I'm running a 7.8" crank pulley and 3.33" blower pulley, so 5800 rpm puts me round 47k, 6,000 rpm would be 48k.
I ordered another 2bar map sensor which I'm going to wire in to a spare ADC so I can log boost pressure before the IC. This will give me an important piece of data.
I am in the same boat with the missing boost. With my 7.8 lower pulley and 2.75 upper pulley at 6500 rpm I get 23 lbs at the outlet of the blower and 13 at the motor, which is a loss of 10 lbs. When I take the intercooler out of the system I only pick up 3 lbs to 16lbs. If you are running a 58mm throttle body like me, I think that is some restriction.I need to put a vacuum guage on the throttle body to see if I get a vacuum to be sure.
It is hard for me to except that I am loosing 23 - 16 = 7lb loss of boost through the piping but it is what it is. I am running a garret core intercooler with 3 inch inlet and 4 inch outlet. IAT temps are 104 at the end of an 1/8 mile run in florida heat, starting at 90 degrees. Without the intercooler, my IAT sensor was maxed out at 250+ so it is removing a good bit of heat. My old ebay 4 inch intercooler would get up to 140 at the end of an 1/8 mile run but I never did a pressure difference test with it. I just thought that was the cause of the restriction, but it was not.
I think you need to spin the blower higher. You can throw the 'blower is turning this rpm, so should get this X boost' out the window when you are using non-stock parts. I think that only applies to stock motors. Put a smaller pulley on it and spin it higher. On my car, I don't pull any timing until 6lbs with the intercooler, but I do run octane boost which is 104 octane all the time in the tank.
Thats weird! You should definitely not be losing that much boost thru a few ft of piping alone! You should double check your map sensor and boost gauge(s) at both spots to make sure they are accurate
You can throw the 'blower is turning this rpm, so should get this X boost' out the window when you are using non-stock parts. I think that only applies to stock motors. Put a smaller pulley on it and spin it higher...
That is exactly it. Boost measures resistance. If Joe pulled the engine and put in a stock TPI system, the boost would increase substantially. But what most don't get is that the higher reading doesn't make the blower more efficient, it's just indicating that there is that much resistance to the fixed air that it is putting out at that RPM. However, if he were to install a stock TPI engine with the blower still embellishing 4 to 5-psi of boost pressure at the same RPM, then yes, there is definitely a restriction between the blower and throttle body. I honestly don't even care about boost pressure anymore, you can tell if the engine is being held back via injector duty cycle. If the power is not there, then there is a problem. If it's there, and you're getting low boost, your engine is just that efficient without the blower. The air from the blower is fixed at a certain RPM, and boost pressure will change depending on the engine's resistance towards it. Turbo's are different, we're forced to slow them down to meter resistance otherwise it will just keep increasing...
I am in the same boat with the missing boost. With my 7.8 lower pulley and 2.75 upper pulley at 6500 rpm I get 23 lbs at the outlet of the blower and 13 at the motor, which is a loss of 10 lbs. When I take the intercooler out of the system I only pick up 3 lbs to 16lbs. If you are running a 58mm throttle body like me, I think that is some restriction.I need to put a vacuum guage on the throttle body to see if I get a vacuum to be sure.
It is hard for me to except that I am loosing 23 - 16 = 7lb loss of boost through the piping but it is what it is. I am running a garret core intercooler with 3 inch inlet and 4 inch outlet. IAT temps are 104 at the end of an 1/8 mile run in florida heat, starting at 90 degrees. Without the intercooler, my IAT sensor was maxed out at 250+ so it is removing a good bit of heat. My old ebay 4 inch intercooler would get up to 140 at the end of an 1/8 mile run but I never did a pressure difference test with it. I just thought that was the cause of the restriction, but it was not.
I think you need to spin the blower higher. You can throw the 'blower is turning this rpm, so should get this X boost' out the window when you are using non-stock parts. I think that only applies to stock motors. Put a smaller pulley on it and spin it higher. On my car, I don't pull any timing until 6lbs with the intercooler, but I do run octane boost which is 104 octane all the time in the tank.
i have been wondering about the connection at the tb on the lt1 car i mentioned above. it has a 58mm tb with silicon connector on it. it has a 4" aluminum tube that has been ovaled out to match the tb connected to it. i know that the long sides of the oval would be a weak spot for sealing, and have wondered if we have a boost leak there. i have not pressure tested it yet.
i have been wondering about the connection at the tb on the lt1 car i mentioned above. it has a 58mm tb with silicon connector on it. it has a 4" aluminum tube that has been ovaled out to match the tb connected to it. i know that the long sides of the oval would be a weak spot for sealing, and have wondered if we have a boost leak there. i have not pressure tested it yet.
I have a 4 inch tube feeding my 58 mm tb with silicone connector also. I measured pressure in the intake pipe after the intercooler (and before the tb) and at the map sensor (after the tb) and get about the same pressure reading. I would think if my pressure after the tb is lower than the tb would be a restriction, but I don't think so.
When i did my boost leak test, i found maybe 20 different leaks. I have worm gear clamps on everything now, from the brake booster connection to the you name it. My biggest leaker was the throttle body. That opening under the TPS sensor and under the spring on the throttle shaft where it goes into the body was this biggest leaker of boost. Take it apart and get some o-rings from napa and put some high temp grease on them and shove them against the shafts. Under the tps sensor, I had to put a rubber washer there to get it to seal. Before I did my boost leak test, I could only get 5 psi in the system and you could hear air coming from the throttle body, now the guage rolls up to almost 30 psi before it blows the leak tester off the outlet of the blower. After spending time fixing all these leaks, I picked up about 1.5 pounds of boost.
That is exactly it. Boost measures resistance. If Joe pulled the engine and put in a stock TPI system, the boost would increase substantially. But what most don't get is that the higher reading doesn't make the blower more efficient, it's just indicating that there is that much resistance to the fixed air that it is putting out at that RPM. However, if he were to install a stock TPI engine with the blower still embellishing 4 to 5-psi of boost pressure at the same RPM, then yes, there is definitely a restriction between the blower and throttle body. I honestly don't even care about boost pressure anymore, you can tell if the engine is being held back via injector duty cycle. If the power is not there, then there is a problem. If it's there, and you're getting low boost, your engine is just that efficient without the blower. The air from the blower is fixed at a certain RPM, and boost pressure will change depending on the engine's resistance towards it. Turbo's are different, we're forced to slow them down to meter resistance otherwise it will just keep increasing...
- Rob
I agree. You can't look at someone else's combo with the same pulley combo and expect the same boost or power. I have a 9.77 inch 10 rib pulley from lingenfelter for a cts-v ls motor here and on the car. I blew a belt off so I need to get the alignment correct before I run it again. I ordered the gates serpentine belt alignment laser tool to get the belt ribs to line up right, as the 9.77 pulley sticks out about 1/4 inch farther than the vortech 7.8 pulley.
Right now I am spinning the 2.75 and 7.8 pulley combo to 63k rpm. I'm gonna spin this bastard close to 75-80,000 rpm and make some real boost.
I don't expect the boost to be the same as some other car with a T-trim, but I had some expectations based on what my calculated n/a intake flow would be. (engine analyzer pro)
Naturally aspirated, my expectation is that the engine should have a potential of 710 cfm at 5800RPM.
Based on the compressor map, I believe (and that may be where the problem lies) that the T-Trim should be flowing about 1150 cfm at 46,000 RPM impeller speed. Since it's a supercharger, assuming there is no belt slip, the airflow should be static at any given impeller speed and we know the impeller speed based on engine RPM and pulley/gear ratio. So let's say 1150 CFM.
I'm at sea level on the New Hampshire coast, so that simplifies math I think.
So if at 1 atmosphere I'm consuming 710 CFM, but I'm forcing 1150 CFM I'd expect the residual pressure (boost) to be 9.11 psi.
Looking again at the compressor map, PR of 1.85 and 47k impeller speed would suggest air flow around 85 lb/min. Does the fuel flow fit with this air flow estimate? 85/11.5 = 7.4. 7.4 lb/min of fuel would require eight 55 lb/hr injectors at 100%. Is it really using that much fuel? That would be enough fuel for 880 hp at 0.5 bsfc.
What's the fuel pressure, injector size and duty cycle at 5800 rpm? You can use this info to calculate the actual fuel flow and multiply by the AFR to convert to air flow. Something doesn't seem to add up here, but who knows if the compressor map can really be trusted.
Ditching the IC should increase flow, but the PR will drop and fall further off the compressor map. The manifold pressure should increase albeit at much greater temperature. Whether or not this will result in more power will depend primarily upon the fuel's detonation resistance. Time to experiment. If nothing else, food for thought.
Tell me about it. I have been trying to find my missing boost for 2 years now and i found most of it. Let me share what i found out. I have a port at the end of the ysi to put a pressure sensor or screw in bung. I have that port going to my boost gauge in the car. I have been fighting this for a long time. When i dyno'd last year, they measured boost at the outlet of the blower at 23 lbs with the 2.75 and 7.8 pulley combo at 6450 rpm. The motor map sensor only saw 13 lbs. That is a loss of 10 lbs. I had a 4inch ebay intercooler that everyone thought was the issue, so a local fab shop made me a garret intercooler from scratch with 3 inch inlet and 4 inch outlet. This garret core is supposed to have less than a 0.5lb pressure drop.
I just did an experiment yesterday where i bypassed all of the intercooler piping and intercooler and ran 3 inch pipe from the outlet of the blower straight to the throttle body. Same pulley combo got me 20.5lbs at the motor map sensor. IAT's are 250+ as my iat sensor maxes out at 250 without the intercooler. With the intercooler, iat's are 90-100 which means the i/c is pulling out 200 degrees of temp which is good. I have run it with a straight pipe in place of the intercooler and picked up 3 lbs, so the intercooler is only costing me 3lbs, but it should be less than that.
I made 13 lbs with that t-trim with the 2.95 and 7.8 pulleys which is why i thought i needed more blower. Turns out it was my intake piping and intercooler the whole time.
Take a look at my picture and try this experiment of running the pipes straight from the blower to the throttle body and see what happens. You have to experiment sometimes like was said above me.
So you were losing 10 lbs thru the ebay cooler. Without anything you only lost 3 lbs (saw 20 psi). with the new garrett core you lost 3 lbs over no cooler (Saw 17 psi?)
So you were losing 10 lbs thru the ebay cooler. Without anything you only lost 3 lbs (saw 20 psi). with the new garrett core you lost 3 lbs over no cooler (Saw 17 psi?)
not bad but still more than i would expect
With the ebay cooler and full intake tubing, loss was 10 lbs
With the garret cooler and full intake tubing loss was 8 lbs
With no i/c and no full intake tubing (shortest tubing only) loss was 1.5 lbs. I might be loosing .5 lb from a leak in my boost guage hose as i was playing around with that hose and knew it leaked.
I played around with so many pulley combos that skewed the non intercooler with full piping results, but i still never saw 20.5 lbs like i did yesterday with short intake tubing and no ic.
Hard to imagine that you could lose boost from intake tubing only. I found some stuff on the internet about the expected loss from air drag through intake tubing is about 1 lb per 10 lbs of boost. I have 2 90 degree silicone couplers on my short pipe now that i will swap out for aluminum 90 degree bends and see if that give me back the 2.5 lbs I am missing.
Looking again at the compressor map, PR of 1.85 and 47k impeller speed would suggest air flow around 85 lb/min. Does the fuel flow fit with this air flow estimate? 85/11.5 = 7.4. 7.4 lb/min of fuel would require eight 55 lb/hr injectors at 100%. Is it really using that much fuel? That would be enough fuel for 880 hp at 0.5 bsfc.
What's the fuel pressure, injector size and duty cycle at 5800 rpm? You can use this info to calculate the actual fuel flow and multiply by the AFR to convert to air flow. Something doesn't seem to add up here, but who knows if the compressor map can really be trusted.
Ditching the IC should increase flow, but the PR will drop and fall further off the compressor map. The manifold pressure should increase albeit at much greater temperature. Whether or not this will result in more power will depend primarily upon the fuel's detonation resistance. Time to experiment. If nothing else, food for thought.
Fuel pressure at that moment was 49 psi, injector size is 72.4 @ 43.5 psi matched set, duty cycle was 70.7, however wideband was 10.30.
43.5 + 5.6 is 49.1, so basically fuel delivery is spot on as predicted.
Then get actual flow from duty cycle, 72.4* 70.7% = 51.18 lb / hr. Now if that was a 'reasonable' AFR it would equate to about 818hp, but 10.30:1 is not a reasonable AFR.
I don't know how to calculate this beyond that ?
IAT temp (as measured in the elbow right before the throttle body) reports 70 degrees (which was ambient) at the beginning of the pull and 78 degrees at the end.
Duration of this pull was 3.864 seconds (3,000 - 5931 RPM)
Now I did another pull a few minutes before that, but it was slightly lower boost so I didn't reference it last night. The numbers on this are interesting:
So, one thing I notice is that the intercooler does see about a 8 or so degree temperature rise, but it immediately falls back down to ambient. I'm not sure what my blower discharge temp is, but i've probed around it with the IR gun and I've seen some mixed data. Between compression and the location of the air filter being near the headers, I wouldn't be surprised if the outlet temp was anywhere between 180f and 220f.
I'm tempted to buy a FAST 5volt IAT sensor and hook it to a spare ADC input to log my air temp out of the blower.
I don’t know if it will help or not, but when I test a truck system in my shop I seal everything from compressor inlet to intake manifold and pressurize. Oddly some stuff won’t show leaking at low psi, but will essentially open up as pressure increases. Ive had systems hold 10 psi no problem, but at 20 psi start to bleed. So you can imagine the losses as it increases on a system that is supposed to operate at 60+- psi. I’d still be looking for boost leaks.
Working from the fuel perspective 51.18 lb / hr * 8 injectors * 10.3 AFR / 60 min/hr gives 70.3 lb/min for air flow, which is not too far off that predicted by the compressor map, but still a 15 lb/min delta.
So is there really a 15 lb/min loss due to leakage, inlet depression (due to air filter), an optimistic compressor map or simply differences between the test stand and an actual running engine?
The good news is that the blower appears to have some more range within the 70% efficiency island if you want to spin it up to 50,000 rpm in the current configuration.
Working from the fuel perspective 51.18 lb / hr * 8 injectors * 10.3 AFR / 60 min/hr gives 70.3 lb/min for air flow, which is not too far off that predicted by the compressor map, but still a 15 lb/min delta.
So is there really a 15 lb/min loss due to leakage, inlet depression (due to air filter), an optimistic compressor map or simply differences between the test stand and an actual running engine?
The good news is that the blower appears to have some more range within the 70% efficiency island if you want to spin it up to 50,000 rpm in the current configuration.
I kind of want to add a temperature sensor to get an idea of the outlet temperature from the supercharger. I guess the real question I have is, should I keep the $150 Chinese intercooler and just add some more spark advance, or should I switch to a more efficient here to water intercooler which would also reduce the length of the piping..
I I think that the intercooler is adequately cooling the charge. But I wonder if the core just can't handle a thousand to 1200 CFM of air flow. ?
Based on everything I've read, The outlet temperature of the blower is probably greater than 180°. So the intercooler is probably taking at least 100° out. Is that a significant enough drop in density to account for the pressure loss?
Based on your calculations, You're assuming it's making around 700 flywheel horsepower right now?
I Wonder if I'm already making too much power for the block and I should be concentrating more and reliability..
Wacky test idea (assuming engine can survive hot boost): Connect one end of the intercooler to the blower inlet (using hard pipe so it won't collapse). Leave the other end open to atmosphere. This will draw ambient air through the core with no cooling. Measure the vacuum at the blower inlet/intercooler outlet to determine the pressure drop across the core independent of the cooling effect. Think of the IC as a big air filter. Overall airflow should be about the same.
Bonus points if you remove the hood and drive it around with the IC sticking up vertically.
Wacky test idea (assuming engine can survive hot boost): Connect one end of the intercooler to the blower inlet (using hard pipe so it won't collapse). Leave the other end open to atmosphere. This will draw ambient air through the core with no cooling. Measure the vacuum at the blower inlet/intercooler outlet to determine the pressure drop across the core independent of the cooling effect. Think of the IC as a big air filter. Overall airflow should be about the same.
Bonus points if you remove the hood and drive it around with the IC sticking up vertically.
That would be a lot of work lol.
I might just swap over to an air/water core over the winter. Would reduce a bunch of pipe and bends.
I have one in the shop, although I don't know what it's flow rating is.
I think I will order the FAST 5 volt IAT sensor though, and plumb that in right after the supercharger. I'm curious what the actual temp rise is, plus I could use it to determine better filter placement.
What's your setup look like on your C4 these days? I know when I ran the powerdyne on my C4 I had some serious heat issues with the proximity to the headers:
I've toyed with the idea of putting a reverse rotation supercharger on my LT1 C4. The compression is probably a little high (10.98:1) but they seem to draw air directly from the c4 airbox when they are mounted backwards. Which is nice.
I might just swap over to an air/water core over the winter. Would reduce a bunch of pipe and bends.
I have one in the shop, although I don't know what it's flow rating is.
I think I will order the FAST 5 volt IAT sensor though, and plumb that in right after the supercharger. I'm curious what the actual temp rise is, plus I could use it to determine better filter placement.
What's your setup look like on your C4 these days? I know when I ran the powerdyne on my C4 I had some serious heat issues with the proximity to the headers:
I've toyed with the idea of putting a reverse rotation supercharger on my LT1 C4. The compression is probably a little high (10.98:1) but they seem to draw air directly from the c4 airbox when they are mounted backwards. Which is nice.
-- Joe
Do a boost leak test and spray soapy dishwater on all your connections and vacuum hoses/lines like was mentioned. I had leaks on every vaccum hose. I have a guage on my boost leak tester and can see how much pressure is in the system and how fast it is bleeding off.
Then put a straight pipe in place of the intercooler before you swap intercoolers and see if you pick up boost. Pull back timing though, I only ran like 14 degrees with the hot 250+ iat temps and I picked up 3 lbs.
Those 2 things should give you more info at the very least.
08-17-2020, 10:02 AM
