How much boost before race gas?

[2543arvin]

Okay, if you dont know, please dont reply.....I dont need any guesses that could cause me mess something up.

Alright, Im running the CT26 w/ the 57 trim and as of now Im running 14 psi without a boost controller. My AVC-R will be here soon and I want to redyno the car with it. How much boost could I run on the 57 trim before I need race gas? How much boost should I run on race gas? Also, what octane of race gas are you guys using? Im looking for a good HI and LOW setting. Im hoping somebody has some knowledge on this matter that I could take to the bank with.

Thanks,
Brandon

 

[radiod]

I'm curious to know the question to this myself. I've got a very similar setup to you, minus the fuel system upgrades, so I'm hitting fuel cut right around 11-12psi depending on the weather, but I'm hoping to fix that this season.

Right now I'm typically running 94, but 91/92 doesn't seem to cause any pinging or knocking when I'm boosting at 11psi. I've got friends that run Skyline GTRs off 94 at 18psi, but then again, completely different engine.

 

[2543arvin]

That reminds me, I forgot to mention that I run 93 octane daily, so that is what the LOW boost would be running from.

 

[Datsrboi]

You don't need race gas. Especially IMO when tuning you do not need it if your car is a daily. Its not like your going to drive on race gas every day. Tune it to the setup you will drive with everyday.

 

[2543arvin]

You don't need race gas. Especially IMO when tuning you do not need it if your car is a daily. Its not like your going to drive on race gas every day. Tune it to the setup you will drive with everyday.

I will have two different tunes. One for race and other for street. They will go along with my HI and LOW boost settings.

 

[IJ.]

Too many variables for anyone to "guess" on this.

 

[2543arvin]

Too many variables for anyone to "guess" on this.

Could you specify the variables?

 

[IJ.]

Static comp
IC size
IC pipe routing
Ignition timing
Exhaust
Ambient temp
General condition of the car
Dyno operator

The list goes on.

A good operator will be able to baseline your car on pump using electric ears to listen for detonation and tell you where your pump limit is then the process needs to be repeated for higher octane fuel.

Keep in mind if you're cruising around on high octane with low octane ignition settings you're making less power than if you had low octane fuel in it.

I prefer to tune to how the car will be driven not some wank factor dyno queen tune.

 

[MRSUPRA]

I ran 17-18psi on 93 for years. I had a stock bottom end with a 2mm headgasket and similar mods to what you have. Before I replaced my engine, I tried boosting over 20psi on puimp gas to see when I could start hearing knock. I was surprised how well it ran until about 21-22psi- that is when I could hear it start knocking.

 

[MKIIINA]

ive been running 18-20 psi on a JT61GT and VPC combo for over a year and before that a similiar setup with the LEX/550s combo. No issues.

Honestly you don't need race gas for your level. the 57 trim and the lex/550s wont let you get to a point where it would matter. sorry dude.

 

[selfinfliction]

why not run meth/alky/water injection instead of race gas? it's cheap as hell (after the kit of course) and i get no kr with that running, the same as with 108 fuel in my other car.

i can't believe more people don't run that here, especially being a turbo engine. would probably drop ait's by 50+ degrees if installed after the fmic.

 

[IJ.]

why not run meth/alky/water injection instead of race gas? it's cheap as hell (after the kit of course) and i get no kr with that running, the same as with 108 fuel in my other car.

i can't believe more people don't run that here, especially being a turbo engine. would probably drop ait's by 50+ degrees if installed after the fmic.

Pardon?

 

[americanjebus]

i run like 15-16 psi on the 57 trim on pump 91-92 octane daily when i drive the car.

i have the fuel, IC, and tuning mods though to make sure im still within stoich range though.

 

[simpsons7s]

I agree with IJ get your best tune to daily street driving, your setup dosen't sound advanced enough to have dual tunes. Unless you are going for a one time wank factor dyno tune, don't even waste the dyno time trying to figure out how far to boost on race gas vs. pump.

 

[GrimJack]

i can't believe more people don't run that here, especially being a turbo engine. would probably drop ait's by 50+ degrees if installed after the fmic.

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

 

[SupraMario]

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

LOL i was just thinking about that.

I wonder what such a negative temp would do to your car.

 

[IJ.]

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.

 

[2543arvin]

Static comp
IC size
IC pipe routing
Ignition timing
Exhaust
Ambient temp
General condition of the car
Dyno operator

The list goes on.

A good operator will be able to baseline your car on pump using electric ears to listen for detonation and tell you where your pump limit is then the process needs to be repeated for higher octane fuel.

Keep in mind if you're cruising around on high octane with low octane ignition settings you're making less power than if you had low octane fuel in it.

I prefer to tune to how the car will be driven not some wank factor dyno queen tune.

Okay, Ill try to fill in the blanks to see if that will help....

Static Comp-If this is the compression of the motor, then I have 9:1 pistons and a 2mm MHG. Im not too sure if someone would be able to calculate the compression from that.

IC Size- 24x12x3" with 2.5" end tanks

IC Piping- 2.5" Hard pipes routed the same as stock.

Ignition Timing- 10* right now, but unsure what timing to run with race gas.

Exhaust- 3" DDP and test pipe, 3.5" catback

Ambient Temp- Given the time of year, Ill use 50* here in NC

General Condition- Rebuilt 4K miles ago and all parts are as new or newer.

Dyno Operator- Not too sure what you mean here.....
With these circumstances listed above, what kind of boost could I run before using racegas?

I understand that there is no point in tuning for race gas if its a daily driver. But I plan on having a HI/LOW, Track/Street, Racegas/Pump setting. Im looking to have a tune for the track to run high boost with racegas, and have a tune for the street running low boost.

It is my understanding that the 57 trim could make ~450 rwhp at 22-24 lbs of boost and I dont feel that is safe on pump gas. Correct me if Im wrong though. Would anyone else run that much boost on pump?

Thanks,
Brandon

 

[Poodles]

I doubt you'll get up to 20PSI without hitting fuel cut...

 

[2543arvin]

I doubt you'll get up to 20PSI without hitting fuel cut...

Well, as long as there is enough play in the LEX AFM screw and my A/F ratios look good, I will try. Right now I have plenty of play left in it.