How much boost before race gas?

[GrimJack]

Dude, the calculations to figure this out would require precise measurements of all the factors IJ mentioned, plus another hundred that he DIDN'T mention, then about a month of computer time just to enter the equations, then another day to actually run them. And after you were done, the error range would *still* be too wide.

Your only option is to take it to the dyno with street fuel in it, have them tune it, store the settings, pump out the fuel, put in race gas, have them tune it again, store the settings, and now you'll know.

Something as simple as the ambient temperature, pressure, or humidity will make what's safe for me on a daily basis very different from what's safe for you.

We can GUESS if you like, but the accuracy range of our guesses isn't going to be very fantastic either.

 

[IJ.]

^ Bingo!

 

[2543arvin]

Dude, the calculations to figure this out would require precise measurements of all the factors IJ mentioned, plus another hundred that he DIDN'T mention, then about a month of computer time just to enter the equations, then another day to actually run them. And after you were done, the error range would *still* be too wide.

Your only option is to take it to the dyno with street fuel in it, have them tune it, store the settings, pump out the fuel, put in race gas, have them tune it again, store the settings, and now you'll know.

Something as simple as the ambient temperature, pressure, or humidity will make what's safe for me on a daily basis very different from what's safe for you.

We can GUESS if you like, but the accuracy range of our guesses isn't going to be very fantastic either.

Good to go, I will try it at the dyno then. How will I know when I am running too much boost for the pump gas? Or should I not chance it and get a street tune at 15 psi and then dump the fuel like you say and get a tune for race gas?

Sorry for trying to pry the answer outta you. Didnt mean to come off like that. Just curious about how much boost I should look for and how much boost to stay away from on the pump gas.

 

[GrimJack]

Start low, (like ~8psi) and keep turning up the boost until any of the following happen:
- Your EGT climbs too high
- You start to detect knock
- Your AFR starts to get lean

The tuner should know this process exceptionally well.

 

[2543arvin]

Start low, (like ~8psi) and keep turning up the boost until any of the following happen:
- Your EGT climbs too high
- You start to detect knock
- Your AFR starts to get lean

The tuner should know this process exceptionally well.

Thanks for your help Grim.

 

[IJ.]

I already posted how the dyno operator should proceed.

Unless you have a good slush fund to rebuild after finding the limits each time there is no other way.

 

[Poodles]

even then, tuning should still be conservative for real day use...

hot day, bad gas, uphill... well, you get the picture...

 

[quake]

there are many variables to this question as grim, and ij stated. It's not the type of thing you want to find out on the street. Assuming a good tune i believe after 15psi is when you seperate the men from the boys. Most important factor here is "pump gas" i believe there are many factors with pump gas. For ex: take from Dr. jones 06-02-2007, 05:22 PM #16
drjonez
Official SM Expert: Piggyback Engine Management
SM Contributor




Join Date: Mar 2005
Location: the motor city
Posts: 2,864
Re: 20psi on pump gas, if you dont know, dont answer...

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eh.

to answer the orig question, sure you can do it. but the better question is WHY? sure you can get away with a myriad of stupid things for a while....but eventually you're going to get a bad tank of gas, etc. and you'll be crying about a fried piston.

i tend to lean towards conservative tuning. why? because there are too many variables out there....you have to consider the one time it's 95F out and you get some bad gas and you decide to race that crapmaro next to you @ the stoplight.

while i agree boost pressure is meaningless, you have to look at intake temps and effective compression ratio. in my book pump gas is fine for 15 psi....much beyond that and it's time for more octane.
__________________

 

[quake]

also keep in mind this is a car with a stock ecu and no timing control. Pick up a knock link or some sort of knock monitoring
device. Ij has some experience with this and will be the first to let you know the 7m is a noisy engine.

 

[selfinfliction]

Pardon?

spraying alky injection in the intake after the intercooler would probably drop air temps about 50 additional degrees. i've seen a 60 degree difference on a turbo motor before with nothing but water injection. the cobalts have about 5 billion sensors... (have an aeroforce gauge which is about 30 different readings in one gauge, reads from obd port) with a 2.7 pulley (18.5psi) doing a wot run in third would heat the charge temps up to 150+ normally. doing that same run with water injection running on my car would keep that 3rd gear run charge temps to a max of 115 as long as it had a spacer and was spraying between the blower and motor.

water injection helps out more than people give it credit for, meth/alky water mix injection helps out even more

 

[selfinfliction]

Err... that would put my air intake temps well below freezing...

uhhh lol. yeah i'm not used to the air to air stuff. we use liquid aftercoolers on our blowers. they definitely don't get that cold... sorry for not knowing air to air got that cold

 

[quake]

liquid cooling works fine when it is working. If you tune the car for it and a pump fails, a line freezes, a wire comes loose, no fail safe system, then you get to loose a motor.

The name of the game is power and once you get it you're hooked. The best (for most) on this forum is to go for the most you can make on pump fuel. This is how the car will be used day in day out. Allways opt for the bigger intercooler, the better tuning system, the more efficient turbo. Your goal here is to optimize your saftey margin with ever changing pump fuel and weather conditions.

If you go for water/meth injection get a kit that allows you to test the system at start up.

 

[selfinfliction]

liquid cooling works fine when it is working. If you tune the car for it and a pump fails, a line freezes, a wire comes loose, no fail safe system, then you get to loose a motor.

the liquid cooling i was reffering to was the liquid to air colling systems that consist of a heat exchanger, aftercooler (pretty much a heat extractor with fins) that mounts inside the manifold, it circulates and looks just like an additional radiator. the water injection is just additional for us.

 

[SupraMario]

Mario: Some guys here are messing around with a dry ice IC and start their pulls at 0 by the end of the run it's -6c.

They think it's upsetting the fuel mixtures and the BoV keeps freezing open if they lift during a run.

is that good or bad?
lol
sorry still learning

 

[IJ.]

Mario: Guess it's good if they can get it all sorted, it's just not a practical system for me as you have to pack it with 30>70 KG's of dry ice when you want to make big numbers. (last time I watched it they were around the 1300+rwhp)

Arvin: I'm just wondering why you want to run your motor to the ragged edge with that little turbo?

There "might" be 50 rwhp to be had it's just not a big enough difference to risk venting the motor and having to start again. (take it from someone that's explored the limits a few times it's damn expensive)

 

[SupraMario]

Mario: Guess it's good if they can get it all sorted, it's just not a practical system for me as you have to pack it with 30>70 KG's of dry ice when you want to make big numbers. (last time I watched it they were around the 1300+rwhp)

Well big numbers and 30>70Kgs of extra weight or decent numbers and not the extra weight.....hmmm

 

[IJ.]

Not to mention the PITA of packing the thing and knowing you can't run that tune daily (car is being built for dyno comps)

 

[Doward]

Ignore your boost pressure man.

If you really want more power out of that turbo, set the pressure to 15psi, tune it for that, and look into porting the head, getting cams, porting the exhaust manifold, etc.

An engine is an air pump. Minimize flow loss.

As for what boost etc, only you and your dyno operator can decide that. I prefer to maximize air flow, rather than increase boost.

 

[mdr40z]

if you want that turbo to live very long I wouldn't set up much past 15, they are just not that strong of a turbo anyhow

 

[MKIIINA]

if you want that turbo to live very long I wouldn't set up much past 15, they are just not that strong of a turbo anyhow

please lets not get into this kind of a pissing contest. the 57 trim ct is a very good turbo for most people.