20psi on pump gas, if you dont know, dont answer...

[Reign_Maker]

This is a pretty serious question, so if you dont know, dont answer... If you "think" dont answer... If you knew a guy that knew a guy, dont answer... If you've never personally done it, or dont have a clue, dont answer, I'll just delete your post...

You guys are fairly familiar with my build, if not, here it goes:

ARP mains, polished balanced crank, eagle rods, wiseco pistons, 20 over, fully ballanced rotating assembly, 2mm TMS mhg, ARP head studs to 85psi, OS valves, P&P head, 1000cc RC Eng injectors, GT4067R turbo, AEM EMS........ and other stuff...

Im running an HKS 40mm external w/g with a 20psi spring... Will I be able to, with my set up, and a proper tune, be able to run 20psi on pump gas, 93oct, daily...

I know that its not a good idea to do 20psi on pump gas with a smaller turbo, like a 60-1 CT26, but would it be ok on a 67mm turbo? I ran my last set up @21psi on pump, but never got to drive it much before I tore it down...

The reason why Im serious about this question is because, obviously, I have a LOT of time and money invested in this car, I would rather be safe than sorry... I need some people who KNOW wtf is up and can guide me in this so I can either enjoy my 20psi weekend monster, or if I should pull the spring and put in a softer spring...

Thanks guys...
Jake

 

[dbsupra90]

i think what you will find jake is it wont run 20psi at the manifold on that spring. you will probably see about 18.

that being said, 20psi is doable, depending on tune. if you have it tuned on the rich side you can get away with it, but still a little higher than id be comfortable with. usually we try to stay 17-18 range on pump gas. and, like i said thats what you may end up seeing w/ that spring anyway.

this is all assuming you have stock compression. if you have lower than stock, you can push it a little further. if higher than stock, you may want to rethink it.

one last thing, toluene is fairly cheap and will add some octane. you could consider running that with pump gas to give a little extra safety margin.,

 

[MK3Brent]

I stay at 16-17psi on pump gas GT4088 160-165psi compression per cylinder, Jake.

How much timing you give it, and how much heat & pressure will have alot to do with detonating.

 

[Reign_Maker]

DB, I was thinking about maybe even putting a gallon or two of 104 in with the 93 to up the oct... I know oct boosters are shit...

You "hear" about guys running 20-22psi on pump... I dunno... I just want to be safe, thats all...

 

[MKIIINA]

ive been running 20 psi on my jt61gt for some time now w/o issue never have run race gas, only 91-93 depending what i can get. if you are that worried that gal or 2 of race gas should help things.

 

[MK3Brent]

Seems with your AEM EMS, you can get a decent timing curve to accommodate 93 octane. Just monitor knock.


Hell, just get alky control and run pump gas for the rest of your life.

 

[Idealsupra]

short answer based upon you wanting to be safe etc jake: NO.

to build on that...why in the hell do you have a 20psi spring installed for a 67mm turbo? that makes no sense...im sure as shit thinking that turbo is swimming in shark infested waters OFF its efficiency island well before 40ish psi...

rule of thumb would be run a spring half the total of your max boost.... something in the area of 13-15psi would be your best bet spring wise.

 

[bigaaron]

I would say that 17-18 is about the max to be safe with 91 octane and a big turbo.

 

[Idealsupra]

I would say that 17-18 is about the max to be safe with 91 octane and a big turbo.

exactly... (although we have 93 here...we arent in nazi CA )

you have to take into consideration temp changes and everything else...i PERSONALLY wouldnt run ANY setup with ANY tune (sans a drag car) more then 18psi on pump gas. PERIOD. theres a WHOLE lot that could go wrong and why chance it for an extra 20hp.

 

[MK3Brent]

I'm guessing strong spring pre-load.

 

[Wills7MGTE]

Couldn't he use methanol injection since its a natural intercooler and this would push the risk of detonation down drastically. Isn't detonation really the only limit other than fuel, so assuming fuel is there then cooler charge temps out to decrease the need for the higher octane fuel. I'm not sure though, could he run a mix of 93 with like a few gallons of 100 or something?

 

[Doward]

That's the t04r wheel, yes? 67mm inducer/84mm exducer? Same as the PT67? If so, here you go -

(182.5ci * 7200rpm)/3456 = 380.208cfm of airflow. I'm going to say you should be around 90% VE, so 342.1872 cfm.

(20psi + 14.7psi)/14.7psi = 2.36 Pressure Ratio - Therefore, you are flowing 807.562cfm aka 55.80 lbs/min of airflow moving through your engine.

El Mapo dell Compressario for you:

Not accounting for intercooler efficiency, you should be around 73% efficiency with that turbo @ 90% VE @ 7200rpm on your .020" overbored 7M.

If you want, let me know what A/R your turbine section (and trim wheel) you've got, and I'll plot you out an idea of how the turbo will work for you.

That said, you've got PLENTY of fuel, and standalone so you should have no problem running 20psi of boost on pump gas - ESPECIALLY if you are still on the stock cams!

Remember, boost is resistance to flow - the proper frame of mind for you Jake, is can I run xxx rwhp daily on my setup.

My advice - get her on a dyno, and ensure that your timing is MBT.

 

[bigaaron]

That is very true, it's easy to get hung up on boost numbers that are pretty much meaningless, when the goal is to make more horsepower with less boost.

But in this case, since he can't go below 20psi because he has a 20psi wg spring, he wanted to know if it would be ok. 20psi is too much for the low boost setting on street car, imho.

 

[Idealsupra]

i just dont see the reward being greater or even equal to the risk.

WHY?

can he run 20psi on pump? with a solid tune YES.

is it a good idea with all the variables in play? hell one bad tank of pump gas and guess what....

jake its just not worth it. the end.

 

[tissimo]

Yes with a good tune

imo i would run less though.. 20 psi and long highway pulls doesn't go together very good.. lots of heat and things cam happen.. (f&h going to texas )... pump gas is too inconsistant to run it to the edge like that.. on my street tune I want to beat the hell out of the car and not have to worry at all.. I can do a road coarse, do a 160+ pull, do some doughnuts or drifts or something and not have to worry.. so i would run less and keep it safe.. thats my opinion.. engines are expensive.. I would keep timing a few * back from mbtt

 

[drjonez]

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.

 

[Mr.PFloyd]

quick question, on a 60-1 ct26, is it safe to run 18 psi on 94? thats what i have access to.

 

[Doward]

On a Lex/550 setup? No.

On a standalone? Maybe.

 

[Mr.PFloyd]

On a Lex/550 setup? No.

On a standalone? Maybe.

maft pro.

 

[drjonez]

quick question, on a 60-1 ct26, is it safe to run 18 psi on 94? thats what i have access to.

no.

sunoco gas is far too variable to push it that far.