Hi guys, I just wanted to get your opinions about boost on a high CR motor.

My tuner says that its physically impossible for a motor sporting 10.5:1 CR to run 10psi of boost. Im wanting to get him to tune my autronic, and even with that he says its going to be physically almost impossible in his word.

Apparently the pressures in the cylinder at 10psi of boost with a CR of stock b16a at 10.5:1 is too high and cant be done even with alot of retarded ignition.

I hear about stock motors being able to run in excess of 12psi, i just want 10, yet he says it cant be done.

Does anyone have thoughts on this?

 

there was a thread not too long ago about the benefits of low CR vs high CR. try searching, i'm sure it's there. HTH

 

10.5:1 will accomodate 10 psi if tuned well and you're using high octane gas.

I'd say find a new tuner.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by freakie &raquo;</TD></TR><TR><TD CLASS="quote">Hi guys, I just wanted to get your opinions about boost on a high CR motor.

My tuner says that its physically impossible for a motor sporting 10.5:1 CR to run 10psi of boost. Im wanting to get him to tune my autronic, and even with that he says its going to be physically almost impossible in his word.

Apparently the pressures in the cylinder at 10psi of boost with a CR of stock b16a at 10.5:1 is too high and cant be done even with alot of retarded ignition.

I hear about stock motors being able to run in excess of 12psi, i just want 10, yet he says it cant be done.

Does anyone have thoughts on this?</TD></TR></TABLE>

get a new tuner..i wouldnt trust that guy to tune my ****, especially autronic when he says **** like running 10.5cr and 10psi is impossible

 

the problem is that he is autronics number 1 man. he said that he would need to be proven wrong, but he has found it pretty much imposssible

 

who is he?

 

maybe ben strader can chime in on this

http://www.efi101.com

 

yeah well i im'ed ben, but he hasnt replied. i hope he does soon.

 

10:5:1 here with 14psi on pump and up to 28psi so far on c116. No problems yet. It is deffinatlly possiable but I would find someone else to tune it.

 

People get a missconception reguarding C/R vs PSI to determine what is safe.

First, what does safe mean? Basically, safe just means its not knocking.

How is knock caused? is it from pressure? Nope, its from pockets of endgass still not haveing the flame front reach them in time before temp/pressure grow to a point where they flash/spontanious cumbustion, and this all happens long after the spark hit of course.

Anyways, what i am getting at here is this, the design of your piston and your cumbustion chambe play big factors in determining when an engine is going to knock. More then C/R and psi. I can make an engine knock at 8:0 NA on pump, or make an engine have 11:1 and 20psi on pump and not knock. If your squish area is optomized, its often called "artifical octane" due to its ability to reduce knock much like running higher octane fuel. If you have dished pistons with pleanty of places to trap endgass and minimal squish, you will be more likely to knock. This is why piston design is crucial to making an engine work well. If you had rollerwave pistons, 10.5 and 10-15psi would not be an issue, not because its strong enough to withstand some knock, but because it will not be knocking.

Also, when you say 10psi, it doesnt do anybody much good unless we have a temp or turbo compressor map to look at. 10psi on a 9b will be 10times more likely to knock then 10psi from a gt35.(just showing some opposite extreams here)

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by freakie &raquo;</TD></TR><TR><TD CLASS="quote">the problem is that he is autronics number 1 man. </TD></TR></TABLE>
Ben Strader is the #1 Autronic, Motech, Holley Commander, Motortron, AEM, FAST and anything having to do with EFI. PERIOD. Why do you think manufactors are having him do all the dealer programs and curriculum?

Now, Steve Nicholos is the US distributor for Autronic. BTW, Ben is in florida for the EFI University 101 class on thur-Friday and the advanced class on Sat Sun. Mase will be EFI 101 certified..hehe

art

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by freakie &raquo;</TD></TR><TR><TD CLASS="quote">
My tuner says that its physically impossible for a motor sporting 10.5:1 CR to run 10psi of boost. Im wanting to get him to tune my autronic, and even with that he says its going to be physically almost impossible in his word.
</TD></TR></TABLE>

Your tuner is an idiot. I guess he has never seen a boosted 350Z, S2K, ITR,, ot anything like that?

 

YOUR TUNERS A JASCKASS, look at joetechs hatch, i want to say it has 12:1 running 42 lbs and run 8 in the 1/4. and this is a gsr motor (not stock but....)

 

Also running on methanol and not street gas. Not saying it can't be done you just have to have a good tuner.

 

It can be done, period. I wouldn't push it too much farther, In my mind, 10:1 is ideal, especially if your on pump gas, but again, it CAN be done. It's not rocket science, just get your a/f ratio right around 12, and pull timing until it doesn't knock. That's all. That's how you tune anything. If enough timing is pulled, it will run great and reliably.

Good luck.

Oh yeah, and the trick is, start with very LITTLE timing, and advance a part of the map at a time. Listen very carefully, tune until the slightest knock is heard, back off a tiny bit, and that's where you keep it. A dyno chart, unsmoothed, usually will do very well at showing even unaudible knock. It looks jumpy on teh chart.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by freakie &raquo;</TD></TR><TR><TD CLASS="quote">

Apparently the pressures in the cylinder at 10psi of boost with a CR of stock b16a at 10.5:1 is too high and cant be done even with alot of retarded ignition.

I hear about stock motors being able to run in excess of 12psi, i just want 10, yet he says it cant be done.

</TD></TR></TABLE>

Hahahaha -- Find a new tuner, you could run 15 psi with a stock B16 w/ Autronic (tuned) and the right intercooling and turbo..

Depends on how safe you think safe is, though.

 

what he said was that it would start to detonate prior to tdc/bdc if teh pressures are too much. The physical limitation i think is teh fuel, the amount of pressure applied by compression by the piston wll apparently cause the fuel to preignite. Thus detonation.

I'm hoping that BEN STRADER will be able to help me. I guess once efi uni is done he will...

 

 

I plan on running more boost than that on 10.1 C/R and pump gas. I already talked with my tuner about it. As everyone else said, get a new tuner.

 

bump in the hope that ben will be on soon

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by freakie &raquo;</TD></TR><TR><TD CLASS="quote">what he said was that it would start to detonate prior to tdc/bdc if teh pressures are too much. The physical limitation i think is teh fuel, the amount of pressure applied by compression by the piston wll apparently cause the fuel to preignite. Thus detonation.

I'm hoping that BEN STRADER will be able to help me. I guess once efi uni is done he will...</TD></TR></TABLE>

ok, first off, you should learn what knock is. Secondly, you should tell your tuner to also learn what knock is.

Lastly, if somebody tells you something illogical, like, knock happens before spark from pressure, ask him how retarding timing would have an effect on knock if it occurs before spark anyhow.

Pre-ignition is something that occurs at very low low pressures, often below ambiant, its from having dirty cumbustion chambers or in extreamly rare cases that just suffered prolonged extream knock, preignition can occur from a hot sparkplug gnd or hot edge in cumbustion chamber. It always occurs at very low pressure however because things get more difficult to light as pressure increases. This is why you get performance ignition when you make large compression increases or run more boost.

Knock is a totally different creature, it is caused by the things in my post above.

I hope this helps,
Luke

 

It can be done. Case Closed.
We ran 12.5 to 1 on a race motor years ago and had no problems.

And your tuner is far from the #1 autronic guy.