ZZ3Astro

Well, it runs. I'm not at all impressed so far by the new engine build. Not only am I having a number of issues, but the performance seems to be quite close to the old engine so far. Here are the issues:

1> Over heating... well, so much for the old engine having something wrong with it, it. This new engine runs even hotter. Turns out the LS1 (aftermarket) fans were junk. I back to the factory fans and it does a much better job of fighting the heat, but it was still a losing battle. I then replaced the radiator with a new stocker which helped only slightly. It wasn't until I swung the bottom of the intercooler out and away from the radiator that I was able to drive it and keep it under 200 degrees (forget that if you thrash on it though). Why does this new engine run so much hotter than the old? It's over 100 miles now so I would think the break-in friction is pretty much gone.

2> AFR swings with engine temp. This is an old problem I used to have at the drag strip (this used to be the only place I'd see the engine temp exceed 195 degrees). Once coolant gets over 200 degrees, even with the injectors at 100% duty cycle the engine leans out. When it is cold, the same VE settings will instantly flood the engine full rich. I assumed this was an issue with the old FPR, and now I'm running a different one. No difference in behavior though. As best as I can tell, the fuel temperature is about 115. Injectors around 160 degrees. FPR around 140 degrees. Fuel tank 113 degrees. I've got to get my fuel pressure gauge hooked up to see if pressure is dropping when the temps go up. If so, why? If not, WTF?!

3> My PLX gauge decided to half way crap out. It doesn't come on when you start. You have to shut it off and back on (restart the engine). I've had a ton of smaller problems that I've been fighting non-stop. I was having an ignition issue but I think I resolved it by replacing a spark plug boot that was heat damaged and a new coil. Also I had to move the MSD 6AL to under the battery tray as it was over-heating in the engine bay. This caused a no-start condition. There is so much more heat with the engine and I cannot figure out why. It's standard bore too.

Total pain for sure.. and with seemingly no payoff (performance increase to speak of). It does go ok at 3-4 psi but at 8 it feels like the old engine at 8. And of course that's only when the fuel is acting right, otherwise it becomes a dog. Oh well

SKELITOR117

iTrader: (3)

What is a ZZ3? Not Familear with this engine.

Orr89RocZ

iTrader: (20)

sounds like you have some issues to work with before you notice the gains. No reason is should be running that hot now unless timing is way off or if the block's cooling passages are restricted alittle.

Fuel issue when hot sounds awfully like the many threads here about fuel pumps failing with heat. If you notice the pressure drop when hot then you may have the same problem they are having. Strange you didnt have it before tho, but perhaps it didnt show up until this hotter motor started running.

ZZ3Astro

Well I did have the fueling issues before, but only when the engine gets very hot. The difference being I had to do hot-laps to get it this hot. Now I just have to drive around a while. I'm pretty sure I diagnosed this with a portable fuel pressure gauge before and there was no drop, but I sorta forgot about the problem because I hadn't been to the strip in hot weather in some time. I also cannot remember if this happened with the stock fuel pump or not.. I only remember it with the Walbro.

About to go wire up my new PLX pressure gauge and put this to rest for once and for all.

Drac0nic

What have you done about your timing? You've dropped your compression ratio as well as gone to aluminum heads. Chances are that you need more advance down low. Are your headers glowing?

Orr89RocZ

iTrader: (20)

L98 aluminum heads run alot of advance, just look at stock ARAP timing tables. I've run those on old AFR 190's which are just about the same thing as a ported out L98 head. 38-41 deg in the cruise spots works well and 36-38 overall at WOT on a n/a motor seemed to work for my friends car.

ZZ3Astro

I just put in ARAP values across the board, minus a couple of degrees up around 100 KPA, then scaled up the 100+ KPA boost timing to match. Car does go much better now but it didn't do anything for the cooling issues. Power at 8 psi feels like the old engine at 11 psi. AFR around mid 11's with my quick tune and it won't feel much different at 10.9-11.1. Not impressive at all. I figured on this engine having at least 80 hp more NA, and exponentially better in boost.

As for the heating... Granted I abused it with a few 8 psi runs through one gear, but in 5 mins of driving I parked in my garage at 210 degrees. Sucks.

ZZ3Astro

By the way, there was a HUGE difference in timing.. 10-20 degrees all over the place. I really had hopes this would fix my cooling issues. Time for work, gotta run..

ZZ3Astro

It's a mid-late 90's GM crate engine, replaced by the ZZ4 which is still available I believe.

SKELITOR117

iTrader: (3)

I see. And yes, still a widely used engine available through GM performance.

Orr89RocZ

iTrader: (20)

Dont get discouraged yet.. to be honest, I cant tell much of a difference in a 12psi pass and a 16psi pass in my car, but it could mean a difference of 5mph in trap speed! thats huge at the track. Speed is all relative. When you are expecting alot and have become used to a old setup, the new one may not feel exciting. Track times will tell the story.

Same with my 383. I told everyone it sounds pissed off but doesnt feel as fast as i thought it would. I said it would likely go lower 12's. First pass with rough tune, it went 11.67...so much for that butt dyno.

For cooling, what water pump do you have? I fixed my problem with actual GM LS1 fans with built in shroud mounted as tight to the rad as I could get it. the extra air flow solved my issues. Perhaps yours just needs air flow? Then again, maybe the coolant ports in the block have some build up and restricting flow? Hard to say.

ZZ3Astro

Running a stock replacement water pump at the moment. I check the lower hose tonight to make sure it's not collapsing. Sad thing is, it has found a perfectly acceptable temp range (190-220, well within the stock temp range) that it stays in, but the fuel system issue is really putting a cap on things. Once the engine gets in the 200 range, fuel supply goes away when in boost. I am going to get a custom hose made tomorrow to hook up my fuel pressure gauge and then I'll have definite numbers on what it happening.

I decided I had to turn up the boost a bit more to re-motivate myself. It feels good at 12 psi, right on the edge of feeling fast, but not quite there. Still not enough power to haze the tires at full boost in second gear though.

Block and heads were thorougly cleaned and tanked, not to mention it only had 20k on it to start with. Judging by the temps of the radiator and hoses, there is no problem getting the heat out TO the radiator. My question is where is all of the heat coming from. Lower compression, no overbore, same cubes... I just don't get it. Perhaps because the aluminum heads are transferring more of the combustion chamber heat to the water? Afterall, they do allow you to run more timing/compression vs iron, so that means some of the energy is being transferred away. That would be the only explaination I can come up with. Wife really hates the hot floorboards and so do I. Very tempted to do a light rebuild on the stock engine and put it back in at this rate.

Drac0nic

The power gain could be a lot more subtle. Check your AITs too to make sure you're not out of turbo. Besides that, did you change the T-stat, and are you sure the pump's rotation is right for your engine's accessory belts?

ZZ3Astro

Yeah same pump I've been running for past two years. Here is what I think is going on. First, The stall converter I put in last winter caused the cooling system to be taxed more. Once the warmer weather came around, this caused the original engine to heat up easier. When AC weather showed up, I found I could not use AC without the temps going up too much. This caused me to look for LS1 fans but I ended up with some crappy aftermarket 'clone' fans that just plain sucked. Believing I had improved my cooling by now having "LS1" fans, I assumed things were just going downhill. Oh, and the old engine had been drinking water for a few months as well. Meanwhile, I put this new engine in which runs warmer than the old engine did (and I think because of it having aluminum heads vs iron), which further taxed the cooling system which was now working with inferior clone fans. After reverse-engineering my configuration back to stock fans, the cooling system is now closer to being able to handle this engine under normal driving conditions.

Conclusion, I need more radiator capacity to handle the additional heat being put into the coolant by the more efficient thermal transfer from the combustion chambers to the coolant. Translation: I'm going to go broke fixing this.

I got so burned out on this project that I bought a boat today LOL. A distraction, if you will.

Drac0nic

hrrm, a boat you say? I don't know about that, they are holes in the water you throw money at. Even more money than a car probably. I'd start out simple and replace the stat and maybe the pump if it's a basic iron one. Are you running a stock T-stat? I went down to a 170 in mine, supposedly it's a good compromise for running fuel injection and lowering temperatures. Something else may be to consider trying straight water+water wetter if you haven't already. If your temps drop your cooling capacity is marginal. If the LS1 fans suck get a Taurus or MK8 fan. They really move some air.

zz17iroc

iTrader: (4)

Nice ride man I've been following your turbo build from the start just like Orr89RocZ that car is going to be sick when its done. But don't worry about it you'll fix it! It's always something simple. By the way how old are the fan motors? I remember when I built my 383 I was having the same issues with cooling and it turned to be weak fan motors. So after swapping them out for new ones, all my cooling issue were gone. I'm also still running stock size radiator with no issues. And also it's been a crazy hot summer down here this year. Just some thoughts man.

Orr89RocZ

iTrader: (20)

Maybe a new rad will help some, but more airflow is necessary! That fixed my problems, true LS1 fans with the built in shroud. I think you need a shrouded fan setup, although my 383 never overheated with stock reconditioned rad and stock TPI dual fans....the 401 just couldnt keep cool. It still runs very hot but rarely over 200 deg anymore now that I have a good set of shrouded fans on the rad to get as much air flow through as possible.

zz17iroc

iTrader: (4)

And I can't imagine the amount heat those turbos create under your stock hood! I believe that's why I haven't put my turbo set up on yet, I just want to do it right and that takes cash.

Orr89RocZ

iTrader: (20)

One problem not to overlook is oil temps after running awhile. Turbos get HOT and if oil cooled, the oil gets HOT too. Should run synthetic oils to withstand the high heat loads, and also run an oil cooler to keep temps in check. Alot of the motor is cooled by Oil alone, so keep the oil cool and the rest of the system will be cool.

zz17iroc

iTrader: (4)

Thanks, Orr that's some good info. I'll just add it to my ever growing parts on the shelf.

ZZ3Astro

They do add up but so much fun, especially when 50% of the area of your county is water and it's called Bay county lol.

As for the fans, these are probably the original fan motors. But I don't think fans alone are gonna do it. The shrouded LS1 wannabes didn't do as good as the stock fans. I also added a third fan as a pusher and it made no appreciable difference. Of course that was in front of the intercooler, so I might try that in front of the ac condensor now that the intercooler is moved outward.

Also I may have figured out a downside to ebay intercoolers... they seem to be quite restrictive to airflow that blows through them to cool the charge. When I mounted the pusher on it, about half the air came out around the edges of the fan blades.

sailtexas186548

iTrader: (2)

from what i've read about pushers is that they are not as effective, so the air not all passing through the IC may be normal.

With a puller fan you create a low pressure(think of it like a vacuum) on the back side of the radiator and the higher pressure air between the cooling fins rushes/expands out to fill the low pressure "vacuum" area, so the small spaces between the cooling fins now are at a lower pressure/vacuum then the cool air in front of the radiator so that cool air expands/rushes into the space between the cooling fins. This obviously is a continuous process so the puller fan's are making the air "want" to go through the radiator.

The pusher fans do the inverse of that, they try to FORCE the air through to the other side of the radiator that is full or air. So you have X amount of air hitting the radiator, 30% of it hits the metal components/fins and bounces off or is deflected, the other 70% hits the air in the cooling passages and has to force it out the back of the radiator.

It's kinda like your air filter, if you pull a suction on it tons of air is gonna flow through it, if you aim your compressed air hose on it, a bunch of that air will bounce off.

I got a "free" boat this summer, my room mate and I are going 50/50 on costs restoring it, thats why my car is still waiting on cold side parts :laugh:

ZZ3Astro

Good info on the fans. It looks like I'm going to have to do a fan upgrade and probably a 3 core also. It's manageable as is for the moment, so I'll probably just do fans (known good upgrades, not fake LS1's!).

I just took the boat out for the first run this evening. It needs more prop.. someone put a 17 pitch on it and it has the 1.81 ratio. Has a good hole shot but only makes 43 mph. Looks like a 21 pitch will get me in the low 50's. It shouldn't have less than a 19 on it. Otherwise the nicest driving/riding boat I've owned. Gotta love those 'free' ones haha.. my friend has a $2 boat that turned into a $1000 boat and it doesn't come off the trailer haha.. but sometimes you can find ones worth fixing up like yours.

So aside from the cooling issues, I have discovered I've got some crazy things going on with fuel pressure. I'm seeing less than 30 psi idling (should be at least 34 psi). When I get into boost, the pressure comes up and then suddenly drops. According to my gauge, at 13 psi I often have only 20 psi of fuel pressure!?? Certainly explains a lot about the tuning issues I've ran into with this car, but seems almost unbelievable at the same time. However, the priming pulse brings it right up to 39-41 psi which is right on the money.

Tonight I pinched off the return line and saw well over 70 psi instantly. I swapped back to my original regulator and the only difference was overall fuel pressure increased about 2 psi, with the exact same boost behaviour. Why can't the regulators maintin the correct fuel pressure even at idle, while pinching the return line easily exceeds it? Odd.

Some video of this from last night.. http://www.youtube.com/watch?v=ydiC2...ailpage#t=264s

Drac0nic

Are you running a rail regulator or one that is aftermarket? Another thing to keep in mind is that it could be a weak pump or a restrictive inlet line. A pump may be capable of putting out 70 PSI but that doesn't mean that it can do it with much flow. A fuel pump is not worth risking your engine over, JMO.

Something else I would like to point out is that if you're making more N/A power you're generating more heat. I mean, think about it this way they say on average 1/3 of the energy you produce goes out the radiator. That means if you're making another 50-75HP with out any boost (and more with) that you're adding 50-75hp (or probably about 20-25% more thermal energy into the mix.

ZZ3Astro

Running a Walbro 255 in-tank pump. FPR is a stock rail regulator. I've tried two of those with the same results (except the original one makes about 2-3 psi more). Many possibilities here but the one thing that does not make sense is the lower than correct pressure during idle and normal driving. This problem has obviously been here from the start because my base tune has remained the same from before the Walbro install, throughout the intercooler upgrade and now through the engine swap. I've had to make no significant changes in the idle/cruise tune to maintain good AFR. With the new engine I had to add a bit of fuel across the board, however now that I installed the original FPR, I'm actually too rich at idle from the extra ~3 psi. If I could maintain the correct fuel pressure I'd have to retune the entire map!

Today's experiment involves restricting the return line to maintain about 45 psi at idle, then drive it to see if it falls off significantly under load.

Last night I went to a cruise-in and happened across a 5.0. He had ET streets, full cage, you name it. The smirk on his face was priceless when I eased past him and he soon took the bait... lol http://www.youtube.com/watch?v=UBJpaDloIXY He later told me he was completely taken in by the stock appearance & sound of the Iroc. Only took about 3-4 seconds from the time he took off to the finish lol

Drac0nic

With vacuum on the regulator in theory you can get down to about 35 PSI of fuel pressure with the line on. Does it hold pressure with the line off?

ZZ3Astro

Just took it for a spin without the regulator attached. It does not maintain even 35 psi and it fell off as I went into boost. Decided to upgrade to a Wix fuel filter since it appears to be a volume issue for sure. About to put that on now so we'll know in a bit.

ZZ3Astro

no difference with the Wix filter, as I figured would be the case. Miserable day.. broke two teeth of the boat flywheel because the 'rebuilt' carb float stuck, hydrolocking two cylinders. Uhg.. time for a break I guess

I'm gonna leave it with my friend who has a lift and let him get the tank out. I'm sick of working on this thing.

DIGGLER

iTrader: (1)

the stock engine was overheating before you pulled it as well, correct?

ZZ3Astro

Yeah but I figured out the problem with that after the fact... it had always ran too hot when the AC was on for a while after putting the intercooler in. After putting the 9.5" converter in last winter, as soon as warmer weather came I started having issues with it heating up faster during drag strip passes, but otherwise normal. Once AC weather came around, I found I couldn't run it much at all without getting too hot (before I could get away with it as long as I wasn't sitting in traffic). I switched to LS1 fans (not the real ones but aftermarket ones from a salvage yard) and the problem got worse. The problems seemed to be progressing by the day and I assumed the fake LS1 fans were at least better than the stock fans. Also I was using water so putting 2+2 together I blamed the engine.

During the latest batch of issues with the new engine, I switched back to the stock dual fans and the temps dropped immediately (though not enough). So I am pretty sure the worsening of my cooling issues on the old engine were actually the new fans!

DIGGLER

iTrader: (1)

you may want to get your radiator checked if you havent already. may be gunk'd up inside?

ZZ3Astro

Brand new one just installed :/ no appreciable change except the little bit of change left in my pocket

ZZ3Astro

So here is where I'm at now..

1> The heat issues have taken a back seat to the fuel starvation problems

2> As above, I replaced the fuel filter with a Wix filter, no change

3> Swapped the new regulator for the original regulator, no change

4> Check the fuel pump voltage at the wire going into the tank.. > 13 volts at all times when engine is running

5> Had a custom line made that comes off the rubber fuel feed into 6AN fittings. Had a 3/8" i.d. braided line with 6AN connectors that goes from that line to the 9th injector port on the fuel rail, to which I installed a 6AN fitting. Now I have both the stock front (restricted) hardline plus the new 6AN line to the back of the rail. NO DIFFERENCE.

So now I'm down to replacing the year old Walbro 255 pump. If that doesn't fix it, a for sale sign will.

ZZ3Astro

Tonight's test drive with the new fuel feed saw a record low of 17 psi fuel with 12.6 psi of boost. First time it's completely leaned out that bad. Funny that the worst behaviour occurs after the 'fixes'

Street Lethal

iTrader: (16)

If the new engine is overheating like the old engine, and your running the same Walbro 255 that seems to be breaking down during both instances, then there is your overheating problem. At first I thought you were lifting a head which would cause your overheating woe's, but running that lean would essentially cause the same condition too....

ZZ3Astro

I wish it would be that simple but that is not the case. I won't drive it around if the AFR is lean. The only time it goes lean is in full boost and even then it isn't out of the high 12's low 13's before I let out (until the last couple of tests where I have really stretched it out to see how bad the fuel pressure would get and is the first time it's had severe lean symptoms). Also it doesn't cool off with extended idle even if it's idling at 12.5:1.

Either way, solving the fuel pressure issue won't hurt!

ZZ3Astro

Might have a smoking gun of sorts.. well maybe more like a rusted bullet casing.. NOT what I was expecting but quite possibly the source of my troubles. The sock was oriented directly under the return line outlet. With the Walbro sock, there isn't any orientation that is further than about 0.25" from the return line outlet, but mine was dumping dead center in the middle of the long part of the sock. This could also explain the older issues of losing fuel pressure when the engine was really warm.. hot fuel rail return fuel going right into the pump impeller. Cavitation? Boiling in the rails? Hopefully. While in there, I did go ahead and replace the Walbro with a new one. No other options if this doesn't work!

83 Crossfire TA

iTrader: (2)

It's a nice thought, but if that really should be a problem then wouldn't later LS engines run into it all the time, they have their pumps mounted in a bucket that the return dumps into also.

ZZ3Astro

Drove it this morning (12 am lol) and all signs are positive so far. Had to pull out TONS of fuel to get the AFR to show something other than 10.0. Didn't see the problem increase with temps and the car got into the 215 region. Got it to about 10.7 and added a bit of timing at 6-14 psi (about 1.5 degrees) and it leaned to about 10.9-11.0 as expected. Really feels a lot better and my timing is still very conservative. I think I have 4-6 degrees available across the board in 100+ KPA regions. that 1.5 degrees made a ton of difference so if it will tolerate 3-4 degrees it should feel pretty strong.

I'm running about 23-24 degrees at 5000 rpm at 13 psi.

83 Crossfire TA

iTrader: (2)

So what did you do with the actual return?

I wonder if the real difference is really just sticking a new pump in there. I'm curious, did your rail pressure drop fairly quickly before when you turned it off?

ZZ3Astro

To answer the pressure drop question, after the priming pulse before starting up, the pressure would reach about 40 and stay at 40 for a while before dropping to 39. I never waited long enough to see what kind of bleed-down time it had but it would have taken a long time for sure. Even leaving it for 1 hr, when I would remove a fititng from the rail it would spray fuel.

The mod that I did can be seen in this part of a video I made on my fuel tank removal: http://www.youtube.com/watch?v=RKKUE...ailpage#t=329s

Orr89RocZ

iTrader: (20)

Good deal, hope the new pump solves the issue

project89

iTrader: (1)

heya astro could u post up ut ignition table, i need something to work off of for my car thnx

ZZ3Astro

I can get you the Tuner Studio export file but I think it only works with tuner studio. I copied and pasted my current tune's timing table and exported it to .html so you should be able to copy and paste if you want.

http://www.mentalsocket.com/Iroc87/turbozz3timing.mht

Please keep in mind, this is a new timing configuration that I haven't driven a whole bunch yet. I have no signs of detonation at all however. Below 105 KPA, it is essentially the stock ARAP bin with a degree or two more in the higher rpm areas near 80-100 kpa. Above 105 KPA, this is my old iron headed boost timing table, plus 10% plus some area tweaking (all increases so far) between 3400 rpm and 6000 rpm in the 105-180 kpa area.

Tonight's test runs were phenomenal. The car feels 'fast' finally, and only at 12.5 psi.

ZZ3Astro

BTW, if you are running TPI/Iron heads and stock compression, you'll need my old timing tables. These ARAP numbers are insanely higher than what the iron headed stock engine would tolerate. In fact at 180 kpa and 3100 rpm, the most I could run was 13 degrees. I believe this tune is over 16 in the same spot.

83 Crossfire TA

iTrader: (2)

huh... interesting video (I just wasted a few min watching a few of your videos on the big screen tv ). I still doubt that it was the return, but a messed up pump.

I'm curious- how much hp do you think you can feed with that single 255 and your fuel system? What are you using to get those readouts?

project89

iTrader: (1)

im running an 882 head with popup pistons for 9.2-1 cr its an old 4 bolt main with a forged crank truck motor 882 flows better then the aluminum vette l98 head but the chamber sucks. ill prolly have about max timing of 16* under boost. i really just need something to refrence for the cruising areas to get me started

ZZ3Astro

I think it will support 500 rwhp. I know it will because my friend has done several cars with that kind of power with the same pump. Of course I'll be watching the fuel pressure and if it has problems maintaining correct pressure I will add a second pump.

The gauge system is a PLX. My display is a PLX DM200 (non OBD version) and the modules are the SM-AFR, SM-BOOST/VAC and SM-FLUIDPRESSURE (its for every kind of fluid except fuel though! I have a fuel isolater but that's another story).

It's an interesting gauge system for sure, but does have some issues that will likely never be worked out. It picks up ignition noise, sometimes the display module doesn't boot up and the control pad can be slow to respond. I've recently found the scrolling graph mode to be priceless though, especially now that I can't keep an eye on the gauge the whole time when at WOT. But the main thing I like is it has all info I need in a barely noticeable single gauge. Keeps that 'stock' look nicely.

83 Crossfire TA

iTrader: (2)

It bothers me that especially the vette guys manage to push them so much farther (heck, even my brother in his ford pushed a 190lph to pretty close to that), but that seems to be about the limit that people run into problems with them around here. I have parts sitting around to do it a few different ways (2 255's sitting in boxes, a KB BAP, and I'm willing to spend $ on it if i can have simple, reliable and functional), but I'm not sure that anything will really get me there, and it's enough hassle to do it on our cars that you really want to avoid having to make multiple experiments.

Enough people with a single, even with a BAP seem to run into problems from the get go. Twins seem to be a hassle, especially with the small tank opening on a 3rd gen and there just isn't a good way to do them without over complicating the setup (plumbing, hobbs switches...) and replacing most of the stock fuel system. I kind of want the 340lph (and maybe a BAP) to work and be a quick and simple solution but I haven't seen anyone get significantly better performance out of them than a 255 IRL applications.

That is pretty slick, I like it, are the problems insurmountable? Seems like they center all their info around the 52mm version on their page, I can't even find info about resolution or anything about the 60mm (if it's worth the upgrade...). Not super expensive either. I'm kind of wondering if I could grab one or 2 and fix all my gauge packaging issues in one shot. (If you have a thread about it somewhere just point me at it and I won't pollute this one any worse )

ZZ3Astro

All of my complaints about the PLX stuff center on the display module (DM-200) that I have. Keep in mind you can use standard gauges with the sensor modules as well (they have standard 0-5 volt outputs for gauges, ecm's etc). But as for the DM-200, it's a compromise. You get these amazing features such as peak values, graphs, analog & digital gauges and of course the 4 parameter you see in my videos. On the other hand, you deal with some quirks as mentioned before. I don't have a racecar and I don't want the Iroc to be one, so to me the compromises are worth it.

The only difference in the 60 from the 52 is a larger size display which makes it easier to read. No change in pixels.

Overall I like the fact that I can get this information and display it in various combinations and ways. You can upload a custom boot logo (I made an Iroc one) and you can design custom gauges (however, only ONE gauge for one sensor, and it is EXTREMELY difficult to do!). I decided I'm going to use a video of a girl stripping down and tie it to boost. I believe you get 256 frames, with the frames going from 0 to the max value of the sensor. So the higher the boost, the more she takes off, LOL.