Orr89RocZ

iTrader: (20)

I've been messing around with my car the last 2 weeks since I got home on work trip and had time to work on the car and actually drive it.

Finally got the driveability tune worked out better than it ever was before and I have been cruising for long periods of time with no ill effects and no overheating.

1/4 mile performance is down a few mph and alot of ET due to lazy 60 foots. I cant get the T70's to spool as fast. But it is hot out being July air, so I expected to be down some performance.

I was playing around with the throttle response tuning and first gear stomps from 0 mph to 20 mph rolls and basically seeing what effects airfuel ratio and timing had on the turbo spool response. I was able to add alot of timing to my table in the 0-5 psi range, much more than I used to have this year and even more than when I had T60's on the car. This seemed to help some, but didnt give the effect I was hoping for.

What I am noticing is that my car is a TURD off the boost. An absolute pig. It doesnt make sense either, 400 cubes + AFR 195's + 233/233 .564/.564 cam should make decent power even at 9 to 1 compression.

My converter flashes to around 3000-3200 on motor and when boost rolls in, it is more like 4200 rpm. Now with 295/30/19 street tires, 2.73 gears and 3000 stall, I am unable to spin tire in first gear. As soon as I mash it, car just doesnt feel like its getting up like it should. Even when boost starts coming on, 4-5psi comes in fairly quickly, it doesnt brake loose.

I compare this to my 99 Trans am, 3200 stall, 2.73 car with 315/35/17 drag radials, it will roast tire like nobody's business. Its a mid 12 second bolt on car.

So I am wondering what is the reason for it being such a turd off boost? Would it be the long length of cold side piping its trying to suck in? Stock 78mm LS1 TB too small? Air fuel was alittle lean in those regions, mid 13s to 1 but there aint too much left to pick up if it was 12.5-12.8 to 1

I was at the track the other day and blew my intercooler pipe off on the burnout and didnt realize. I brake stalled to 3000 rpm, saw 0 psi on the boost gauge and went WOT on green light. 1.94 60 foot......thats pathetic for all motor. No boost was made, maybe saw 1 psi which makes it even worse. It just feels like a 14 second car with no boost and I am thinking thats one of the main reasons this setup is not putting out the numbers it should with the new turbos and the boost level its seeing.
I would figure this car to be a solid 340whp on motor setup, possibly more! I dont see why it wouldnt do that with 400 cubes and good heads/decent cam. Certainly aint running like it.

Just thought I'd ask around, has anyone felt the same way about their turbo cars off boost? Even blow a cold side pipe and run for a few seconds on motor and feel soo slow?

project89

iTrader: (1)

honestly it probably isnt a turd, uve just got so used to the power with the turbos,that anything else is going to feel slow.

Orr89RocZ

iTrader: (20)

maybe that, but it still feels alot slower than my 99 TA which is a mid 12 second car and about what I'd expect this motor to do if it was n/a only.

scamaro355

How long has it been since you did a cranking compression test?.. I could see a solid 12's car with like 3.42's and that engine N/A the 2.73's with that converter prolly does hit in the cam's rpm range like you'd expect

Orr89RocZ

iTrader: (20)

i did a cold cranking test but didnt tell me much data since it was cold. I cant get the fitting on to do a hot test on all cylinders but most were in the 140-150 range as expected with a low compression motor

86Z

iTrader: (4)

i would say something is going on, my 305 without boost has no issues roasting drag radials. boost is just crazy

gta324

try putting the airfilter direct to the TB.

My car felt like an old dog this year without boost, changes are wider Drag radials and a really low stall speed converoter, will se how much it will stall with boost. Anyhow just checked my timing and it was 10deg off hopefully it will feel better now...

Orr89RocZ

iTrader: (20)

I may try disconnecting the feed pipe off the TB just to see if it helps the feel, but I honestly think this setup should be stronger than it is On boost it gets the job done, but just doesnt seem as fast as it should be but it could be the turbos are too big for the heads/cam this engine runs.

I wanted to take the turbos off somehow and run an adapter piece to tune the motor n/a to get a great idea of what the power is like and dial in the overall tune. Maybe I'll work on that next time I'm home.

old z mzn

iTrader: (1)

78 mm throttle body is small. not enough air?

Street Lethal

iTrader: (16)

Should still make enough torque to roast the tires, even with the smaller throttle body. Sounds like a timing, and/or ignition issue....

Orr89RocZ

iTrader: (20)

I'm starting to think the cam is in wrong, perhaps too far advanced....i had issues getting it to degree out right and once I got it somewhat right I left it at that and didnt check any other lobes. I may have took readings at the wrong lift points. That may not be it tho, hard to say. I am looking at changing some things out this year.... I want larger heads/cam

TMFK

I would imagine the turbos kill power from the exhaust restriction when you by-pass the intake side.

gbayfisher

That and 2.73 rears!

ASE doc

You know, larger isn't always better(can't believe I'm saying that). Larger heads and cam will give even less low rev power. You know you had more low-mid range grunt with the smaller screws. The larger turbines just take longer to ramp up. You could try a small shot of NO2 to kick them up quicker. I agree that the exhaust turbines as well as the intake plumbing are probably a notable restriction to flow and affect power when you try running NA.

You also have your timing and fuel maps set for boost. You shouldn't expect them to work well on the NA motor.

Orr89RocZ

iTrader: (20)

fuel map is actually very close to being what i'd run on these heads for a n/a motor up to 3-4psi boost. The smaller hairdryers actually did do better. i may swap out to 61's and try those.

Logical choice tho is to get the heads/cam that compliment the 70's to go faster

Drac0nic

Do you have any logs from the EFI system? What are your AFRs doing in the transition? How much timing do you have in before you hit boost?

Orr89RocZ

iTrader: (20)

AFR seems to follow close to 13 to 1 air fuel through the 100kpa to 120 kpa (0 to 2.7psi) range and then it starts to taper down into the lower 12's as it goes through 140-150kpa (6-7psi)and seems to be at 11.5 to 1 most of the way through to 194 kpa and 11 to 1 air fuel above 200.

I have 35 deg at 100kpa which is n/a WOT throttle range, and then tapers off to 32 at 131kpa (4.3psi) and then 28 deg at 6.5 psia then 22 at 8.8psia. tapers off a few degs as it goes up in boost. I can and will add abit more timing since the car didnt pull any. So far I've been running about 13-14 deg timing at 16psi boost. Not alot but its safe. i'll try to work that up abit more. In cold air with the old T60's I used to have more timing in my map at higher boost levels. I gotta get back up to that level again. Probably some power in there.

Doesnt matter tho, it still aint spooling as fast as I'd hoped and still a turd on motor

Anyone want a T70 turbo(s)? I want to go back to 61's this time.

gbayfisher

The motor is the same one you used the smaller turbos on, correct? Was it always on the doggy side? If your bottom can take the added cam/ heads and rpm, it would be cool to see the T70 !

Orr89RocZ

iTrader: (20)

Yeah i kinda noticed it alittle on the dog side when it was T60's but then it had a converter that was way too large for the combo but that high rpm spooled the turbos instantly. So I never really worried about the response in first gear when going WOT.... it was instant then. When I did switch to the current converter, it still spooled really quickly it just didnt pickup ET/MPH like I had thought it would.... But I didnt get to drive that setup much that year as I was plagued with problems.

I'll try disconnecting the TB piping to see if that helps. I'm gonna fab up a bypass pipe and take the turbos off to tune the car more all motor and see what I can get out of it. HOpefully it wakes up.

I got a feeling that trying to breath through 3 ft of 3" pipe and then suck air through an intercooler is not good for n/a power It may wake up alot with just an air filter on the TB.

freaky

wouldn't using a intercooler on a na motor be like a extra cold intake ? i been debating thgis since i have some of my turbo parts in the basement . i was thinking about putting the intercooler on jus to be a step ahead when i put the turbo on .i'm currently running a 3x14 with a open top element an think i'm sucking to much hot air ,so i was thinking if a cold air intake is better then running thru a intercooler would be even better .

freaky

when i'd blow my intercooler pipe off my srt4 it felt slower than my na neon did also but i just figuered it was because of the tune .

Orr89RocZ

iTrader: (20)

Intercooler would just act as a restriction. there is no cooling effect. Ambient air is same temp as inside intercooler air. If it was water to air with ice water, it be a different situation. Sucking air through a long 3" tube is not the same as a short 3" tube. generally the longer the run, the larger the pipe size to account for losses in the pipe walls.

But still, I dont think it would kill things THAT much. Oh well, I got some work to do and some experiements to try.

freaky

hum thats an interesting thought . so the only way a intercooler would help a na car is if you put a nitrous sprayer on it .interesting

Drac0nic

You seem to be focusing by and large on your in-boost and transitional areas. Have you focused much on your totally off boost areas? I don't think I've heard you mention them once except the transitionals. Twin 70s is a hell of a lot of turbo, even with 400 CID and lots of flow you're looking at not being afraid of spinning the enigne some to handle it.

Orr89RocZ

iTrader: (20)

Well I am finding this out now that 70's is alot of turbo and too much for my combination. I am not afraid to spin the combo, i just didnt build it to go alot of rpm as the cam/heads are tiny for a 400 motor.

What do you mean off boost areas? I showed my 100kpa which is atmospheric conditions you'd have in a WOT n/a car. Air fuel is good but a touch lean. Timing is good at 34-35 deg. At launch I'm at 90-100 kpa on the footbrake so there is little transition from part throttle to WOT. EVEN with coldside pipes blown off on one side of the intercooler, the other turbo is connected and I still see 1-3 psi depending although alot of the air is going out the open pipe.

Everywhere else in the curve for cruise and such is fine. car feels normal and cruises very well. I"m just concerned with the WOT performance. WOT in any gear with coldside pipes off, its a dog That is the n/a simulation


I think the plan is now is to go back to 61's and just keep the heads/cam or at the very least, just upgrade the cam. Doing heads/cam/etc and keeping the 70's is what I reallly want to do but its the most expensive way to go and will require alot of retuning and be less streetable than it is.

I wont have time to really tear down entire motor over 2 week period so i'm not sure what to do. I will have to plan this out when the time comes. even 61's on high boost should be more than enough to touch 1000whp



I wish i had video showing the spool time and the effect on rpm. At WOT i do see boost almost instantly... 1-5 psi range comes up fairly quickly but the car isnt moving hard like you'd expect. its not until about 7 psi that it EXPLODES to full boost of 16psi and takes off like a rocket. Its literally like a switch there and you'd probably hear it in the vids. That delay of 1 to 7 psi tho is what is killing the off the line performance, but even then once the turbos are spinning, its still not generating the power it used to with the smaller units.

Dark Ember

I bet the turbos are eating 40hp up. Cause when you arent running boost, but still sending exhaust through the exhaust side of the turbo, its just a completly counter productive back pressure device. Admittably, what you are describing does sound odd. Track test it without any boost at all. Thats the only way to know for sure if your engine really is down some hp from where its baseline should be. Also, turbo engines usually have more ring gap, without boost to create the heat needed to expand those rings, you are losing another 30hp or so depending on who you ask. So, total guesses here, but theres 70hp down just from those 2 factors. *shrugs*

DIGGLER

iTrader: (1)

i would be interested in the 70's if you decide to sell.... if so, shoot me a pm and lemme know.

BBCpoweredZ28

iTrader: (3)

X2

tom86iroc

iTrader: (1)

should get that on a dyno to get a base reading and then go from there

tom86iroc

iTrader: (1)

you should get that on a dyno to get some base readings first maybe they would have some answers too when it's on the dyno sorry double post computers slow today

Orr89RocZ

iTrader: (20)

Dig, PM SENT.

BBCpoweredZ28, you will be next in line if Diggler declines

Tom86iroc, the only time i had it on the dyno was with the smaller turbos and 5500 stall converter. it stalled too high for the combo and I had the converter reconfigured to what it is now ~4200 on the boost. But on the dyno I didnt see the power gains I expected to see as boost increased and it may have been the converter eating some of it. It also didnt seem to peak anywhere near the 5800 rpm I wanted it to and what the cam should have been capable of. Again, it may have been converter that killed that or something else like the cam too far advanced.

In either case it made 640whp on 12.5 psi I think and only 690 on 17 psi but the 17 psi tune was pig rich compared to where it is now.

I track tune and street tune more than anything and right now my air fuel is comfortable for the boost ranges I see and only thing else to play with is timing. I dont think the dyno will tell me anything extra that the ET/MPH at the track will tell me. The first time I had the setup out this year, it was running richer than normal and only went 134 mph. I leaned it out some and it went 137. Leaned again and with few deg timing added and 1 more pound boost, it went 140. It didnt gain as much with more timing/less fuel as it did the first time I leaned it out so I know the tune was getting closer to optimal.

Damon

I apologize for coming in late and not knowing your combo. And certainly I've never owned a 9 second turbo car. Half a second slower and on nitrous is as fast as I've been.

However, I have always had good intuition about these kinds of weird things. Here's what my experience is telling me.....

1. You're right. You should still be able to blow off the rear tires on the street even with no boost. Those who have experience with mild/moderate 400 combos know that a 2.73 gear ain't the crippling handicap it often is on a smaller motor. If the converter is close it will shred the tires to the cords even with a "highway" rear gear. Somewhere in the 12s, no boost, doesn't sound at all unrealistic.

2. SO...... why doesn't it? Good question, right?

3. Are you still running a distributor? If so, you STILL have a mechanical base timing setting to deal with. Have you verified the initial ingition advance at the distributor (no computer advance added)? Have you verified that the TDC mark on the balancer is accurate, that you haven't slipped the balancer or have a balancer/pointer mismatch that is causing it to read inaccurately? Have you verified that the rotor in the distributor is phased correctly (unlikely since that's usually accompanied by audible exhaust popping and misfires, but still worth checking). Is the distributor gear chewed up, retarding the timing and causing spark scatter in the distributor (again, unlikely, but worth checking)?

4. Ignition boxes..... I assme you've got one and with some kind of boost-retard system. I can't tell you the number of times one of these systems has gone flaky on stuff I've worked on. Either the box just goes bad (weird behavior either above or below the multi-strike point around 3000 RPMs on an MSD is common, for instance).

5. OR THIS ONE.... a boost-retard system that's kicking in when it shouldn't- pulling out timing even when no boost is present. This one I've personally run into and it's driven people I know up a wall. On an old MSD system it's an add-on. Unplug it and suddenly the car runs like a raped ape off-boost. (Don't try it like that on-boost, obviously!!) Just bad freaking electronics, basically. No way to fix it but replace it if you find that to be the case.

In general, this sniffs like an ignition problem. Bad injectors or fuel pressure you would see on the A/F gague. Intake restriction you would see on the MAP. Exhaust restriction you wouldn't be able to build any meaningful boost. Valvetrain you would either hear or it would be like like hitting a wall at a certain RPM. None of those are what you're describing. That leaves, for better or worse.... ignition.

Orr89RocZ

iTrader: (20)

I verified base timing a few times before but its been alittle while since I checked it. My balancer seems to be fine and matches the TDC point when I assembled the motor 2.5 years ago I'd have to double check now to be sure its still on.

As far as I know its phased and working like it should. Car runs and sounds great, just doesnt feel like it has the ***** I expected on WOT stomps.

No idea on the dizzy gear. I guess i could check all that.

I have an ignition box but it does not do any boost retard...all my timing is controlled in the ECM. The box does a startup retard but I doubt thats causing the problems. Box appears to function just fine but it is a few years old now. I dont think its pulling timing but theres no way to tell I guess. What I see in the ECM I havent verified at the crank except at idle, I have verified that before and they both matched at 24-25 deg.

If it was ignition I'd expect it to run crappy at high rpms. But every now and then i have had the car breakup on me for no reason and randomly shut off. Thought it was a loose wire connection as it seemed to go away before when I played around with wiring and only happened when engine bay was HOT. WHo knows it may be ignition...i'd have to investigate.

First step will be to fab up bypass pipe and take turbos off, disconnect intercooler tube and run all motor to see how it feels. Tune from there.

Tony89GTA

iTrader: (7)

Try the air filter on the TB, think you will notice a difference. I know when I had mine all hooked up it was a turd also, then I bought a K&N TB filter for n/a tuning, much better after that.

fast82z

iTrader: (1)

You will be excessively slow when blowing off a cold side pipe. The wastegate closes trying to make boost, but the cold side never gets into boost. Now you're ramming much more exhaust through the turbines than normal and have high exhaust pressure without boost in the intake. I had a coupler partially blow off once, but still maintained boost. The car ran much slower, like .5 sec or more I don't exactly remember, just because of excess exhaust pressure. My car can also only muster a 2.0 60' on motor at 3100 stall , but launch on 4psi at 3600rpm and it will FLY.

Orr89RocZ

iTrader: (20)

maybe I was expecting much more out of this than I should have, but only time will tell. I need to get back in garage and make a n/a pipe setup and get this thing running tip top.

Street Lethal

iTrader: (16)

I still say that it is a timing and/or ignition issue. You were running 9.86 at 141 in a car that weighs approximately 3400 pounds, which would place your horsepower a little over 700-FWHP, and that is at 14 pounds of boost, which should give you a little more than half that without the boost. Could be that your timing is off, could be bad plugs, could be the wrong plug gap, could be bad wires, or it could be a bad coil....

Orr89RocZ

iTrader: (20)

141 i thought would be closer to 800-850? It dyno 690 went it went 142mph. Theres more than 10 hp lost through a stalled Th400 And the car is likely closer to 3600 now with me in it...maybe even 3650.

But i'll start looking at the plugs and ignition components. Thanks for the advice. Confirmed my suspicions, just figured I'd ask other guys how their cars feel off boost.

DIGGLER

iTrader: (1)

i think this is the best explanation. when you have a situation where the wastegate is closed and the turbo isnt spooled, you effectively have a slightly restricted exhaust and no boost. kinda like a n/a car with a 2" exhaust. add to that your 2.73 gear. i can see it being a bit of a turd.

Street Lethal

iTrader: (16)

The numbers don't lie though, 14-psi is going to add 95% more air and fuel into the combustion chambers, and the engine will make x amount of horsepower with 14 pounds of boost based on that particular setup. When we take away the boost factor, the engine should be making just under 400-HP, so we can't blame the current setup as some form of hindrance in a naturally aspirated condition, because the engine is still making just under 400 horsepower naturally aspirated, it has to be making that power without boost, regardless of the exhaust. Let's also remember that we don't even know how tall of a tire he is running out back, so the 2.73's may not even be an issue. With that stall, he should be blowing the tires away from a dig, especially on street tires....

DIGGLER

iTrader: (1)

im thinking it would be good for 360-400rwhp n/a through a set of headers. but what would it make if you capped each header with a turbo?

Orr89RocZ

iTrader: (20)

I would hope this setup makes atleast 1 hp per cube as it sits. I originally estimated this setup at 430-440hp crank or 340 whp, same as my LS1 car. Desktop dyno I believe shows the same level but thats not the best estimating tool. But that would be optimized exhaust. And it wouldnt make same power regardless of the exhaust being turbo manifolds or not.... IMO pressure on the intake side well help lessen the effect of reversion into the cylinder. With exhaust backpressure and no intake pressure, theres more exhaust that can effectively get into the cylinder during overlap. Less pressure drop across the valve so less gas can come out. With boost, more intake pressure, it makes things closer to being even from intake to exhaust.

One way to find out is to bypass the turbos with a adapter pipe from T4 flange to downpipe. easy to make and I will do that when I get a chance. If it picks up power then I know its an exhaust restriction off boost.

26" tire out back.

Street Lethal

iTrader: (16)

Bottom line is this then....

What was the trap that run, as that will tell us everything....

Orr89RocZ

iTrader: (20)

like 25 mph.....I never run more than a few seconds when I pop the intake pipes I hear you can overspin the turbos, but not sure I buy into that. I launched it, stayed into it I THINK the entire 60 foot range, and then let out. Coasted, rethrottled to see if it would spool, then saw nothing so i just put it in 3rd gear and slowly drove down the track. Think it was like 20 second ET and 20-30 mph




heres another thought....i run a very cold spark plug for boost.... low compression motor with aluminum heads, and a very cold plug should cost some power. Normally i'd run a 5 heat range or even a 4 like stock for a motor like this if it was n/a. I run a iridium based 8 heat range from NGK

Didnt think of that til now but that could be a reason huh?

Damon

Yeah, I guess ripping the tubos off temporarily and tuning it N/A would definitely start to lay stuff bare.

But..... that's an awful lot of work. And how long does it take you to determine that the off-boost performance is lacking? Maybe half a second from where you bury your foot in the throttle? I mean, how long does your brain take to determine that you've just buried your foot in a bucket of cold oatmeal? Probably not very long.

If you could get the feeling that it's snapping immediately to attention and hauling some a$$ for even ONE SECOND after you stab the throttle you would probably know you figured it out, or were at least on the right path to figuring it out, right?

Maybe if you left everything on it but focussed on the performance in that first second after the pedal meets the carpet. Those big-a$$ turbos ain't spooling in that short time period anyway, right?

I'm not saying anything here. I'm just saying. You know, think about it.

Orr89RocZ

iTrader: (20)

I already did that I have been doing first gear roll ons for a few days before hitting the track. I only did a few seconds burst. mainly 3000 rpm to 3800 right before things started to spool up...i hit about 5-6psi by then and it still didnt feel like it was moving well, because I'm used to 15psi

Main thing I looked for was air fuel ratio and timing. I had a conservative table in the bin and i started adding spark to it. Air fuel appears to be around 13.0 to 1 which is fine, so spark was given in 2 deg increments. If the car didnt pull timing I started adding more. It seemed to help some but not as much as I hoped.

Main reason for fabbing the bypass pipe is so I can do a full pull to 6000 rpm off boost to dial in the rest of the VE table. I've never hit more than 3600 rpm with less than or equal to 100 KPA. Having the entire table tuned will help me determine the engines powerband and dial in the rest of the VE table for the lower boost ranges and high rpms that I have never hit. I've only been able to tune 8.5psi on the wastegate alone all the way to 6K rpms. Air fuel is fine so I tapered the VE table down to match for other lower boost areas. I just want to see if i'm right.

project89

iTrader: (1)

havin those adapters made is a good idea anyways.
i plan on making 2 for my tt iroc this way if im far from home and a turbo happens to blow out a seal or die i can remeove the turbos and still drive home.

Orr89RocZ

iTrader: (20)

I didnt even think of that one, but yes I guess thats a possibility and bypass adapters will be necessary to get home I already carry a spare water pump motor, i guess spare exhaust parts wouldnt hurt

Adamoctober2009

Any body thought about the fuel? Low compression engines dont run as well on higher octane fuel.

DIGGLER

iTrader: (1)

a low compression generator will run fine on 112 octane fuel. heh....