I know it's a bit of a loaded title for a thread but please bear with me anyways. I just upgraded my turbo to the new CBRD BBK Lite unit - very impressed with the newfound urge but now it's time to make it track-worthy!

I'm specifically interested in using my car for trackdays (and AutoX) on a regular basis but since I also like to drive home afterwards with everything in one piece I'm just curious how much boost people think can be safely run on the stock bottom end.

Of course it depends on the tune so for the sake of argument let's assume that the tune is 100% safe. 0 knock, 0 timing being pulled, safe IDCs etc. Stock bottom end with ARP head studs and all the usual bolt ons (cams, springs, retainers, cam gears, intercooler, intercooler piping kit, pod intake, turboback exhaust, fuel pump etc. etc.).

I'm running around 1.85 bar right now (roughly 27 psi) - wondering if that's a bit high, way too high, ridiculous or possibly safe. Perfectly happy to use lower boost - I have some nice settings for 26psi and 24 psi in my phone.

But let's just say that I like to harass faster cars, so power is a nice-to-have.

Interested to hear everyone's opinions.

PS - Fuel is regular 93 octane pump gas - I do usually mix in a litre of pure toluene per tank just to lessen detonation slightly though.

Hope someone has some good input - the only similar info I've found on the forum is the guys with the 30psi, 500hp GT35 stock block setups, which I don't think applies to curcuit racing so much.

 

I'd change over to c16 for track days, and wouldn't run much past 28 psi.

 

I was thinking something similar to this. Or perhaps 100/104 if you're worried about the leaded fuel.

But yeah, it moreso depends on your tune. Running it lower (closer to stock) will definitely be nicer to both the engine and the drivetrain in terms of longetivity.

A straight 'safe' tune for 93oct isn't 100% safe for thrashing at the track as you can always come across bad gas. On the other hand, 100/104/C16 is what it is. If you're tuned for that or use some of it as added safety, I think it's a very smart idea personally.

 

I normally mix in a little toluene (about 1 litre per tank) for some added safety but I'm open to mixing in C16 etc. as well...any idea of what ratio of gogo-juice to mix in or what quantity per tank with 93 octane?

Otherwise still wondering what a safe 93 octane boost level would be though. An extra race gas tune is a no-go unfortunately.

 

Sunoco 100, 25lbs boost all day long....

 

really depends on your tune. your car can be tuned to the ragged edge on pump gas or race gas or it can be conservative and safe so that you are able to drive home.

I run more on the conservative side when I track my car because reliability is more important to me then power. Having said that, I did do a couple sessions by accident with a hole in the line connected to my WG (didn't zip-tie it down and the fan cut a slit in it) which was giving me around 28psi peak. luckly I tuned my car on the conseravtive side and usually spike a gallon or two of 112 with a full tank of 93 oct.

 

On 93oct that's pretty high boost, but if the tune is safe then run it!

For reference, I ran 35psi (FP Red on 110oct) for the last few trackdays in a row and no issues here. 100% stock Evo X longblock...it's all in the tune

 

I agree on the tune thing....and I do like conservative too. We have plenty to offer in terms of cornering speed anyways

I think I'll take the advice on the race fuel if that'd work - as I said I normally dump in a can or two of straight toluene but supposedly that can foul plugs and whatnot...grabbing some race fuel might make a little more sense.

And I'll turn it down to 26 psi just in case

I actually ran 26 psi for the last year without issues but I had the tune juuuuuust right - don't want to be overconfident with the new turbo on there though.

Good advice, thanks all

 

I used to spike my tank with Toluene back in the day when it was around $18 for 5 gallons. Last time I checked, a couple years ago, it was around $48 for 5 gallons. IMO I'd rather have race gas in my tank for a few $$ more dollars a gallon and not have to worry as much about the carcinigenic (sp?) effects of the stuff.

 

Oh, I didn't mention my 93oct tune. I've got a tune for max 23psi and was instructed to run 2-3 gals of 100/104 (ala unleaded) to a full tank just to be safe in case I get a bad tank. Zero problems ever; of course it's a safe tune as I told the tuner I would be using the car for track duty on the weekends.

I've since gotten a straight 100oct tune with a bit more boost to it...

 

For 93 you will want to run 11:1 AFR and you can likely get away w/ 25-27 on your non-stock turbo. This is considering your timing goes from something like 4-5degrees at peak torque to 16ish degrees at 7K.

On the stock turbo 25psi makes a hot track day very inconsistent. Also running leaner than 11.5 will give huge inconsistency at a track day. You can always increase any of these limits by adding or using race gas or additives.

 

This may sound crazy but I actually run less boost on trackdays

 

me too.

 

I think I hold the record at .95bar during trackdays. My lap times are actually faster on lower boost.

Until I get more skill and track time it will stay like that for a long time. The Evo has way more power and grip than I can handle.

 

I'm not totally adverse to simply lowering the boost...but if I can simply add more octane and keep a little more power on tap safely that suits me juuuuuust fine.

I've always wondered anyways, so thought I'd ask people who DON"T blow up their engines every 6 months (unlike some of the local guys here).