Evan70

Given that I run 16.5psi on the street with 93 octane with no problems, could I increase my boost (EBC) if I run 101 or 104 octane at a track day (or on the street)? If so, how much?

Mods:
Lindsey DP wastegate, EBC, Vitesse chips, gutted cat
I've also recently had the headgasket done with a special 3 piece unit, and had the head worked on while it was off.

Helstrm

From what I have seen you should be able to run up to 20psi on 93 octane without a problem.

Evan70

Ummm, and the reason why Vitesse would say "DO NOT EXCEED 17psi on pump gas (93 octane minimum)" would be??? I'm sure I probably could run 20psi on 93 octane, the question is how long? I'm not looking to push the ragged edge, just wondering what is reasonably safe.

TurboTommy

With your stock turbo, you're hardly going to gain any more power, anyway, by upping the boost any more than your current 16 psi.

fortysixandtwo

There is more to how much boost you can run, than the octane rating of the fuel being used. Timing will also play a big part.
To partly answer your question, yes. The higher the fuel's octane rating, the higher boost you can run.

Mike1982

The reason that Vitesse could say that is because at that higher of a boost level you might not have the fuel to keep a good air/fuel. Plus, like they said, with a stock turbo, upping the boost much pass 18, you don't yield anymore HP because of the heat coming off the turbo. If know anything about turbo graphs showing pressure and air it can move, there is a certain range for each turbo that it runs the best, start to get outside that range, and you loose HP per PSI. So, let's say you run 16 and get 240rwhp, then run 18 and get 260rwhp, if you go to 20psi that doesn't mean that you will get 280rwhp at all. With the stock turbo I have heard that around 18psi with those upgrades, is about as good as you will get. Just something to think about.

Evan70

Well, the thing is I'm not even at 18psi right now. From what John has said in emails we've traded, I'm probably about at the limit of the stock injectors right now. I guess I should just go ahead and bite the bullet and get some 55lb injectors and see about running 18psi. The question becomes at that point, will I need to send the chips back to be retuned, or could I go with something like a MAF and Mafterburner software from Lindsey for adjusting the fuel curve?

Russ Murphy

Read this-Octane and Horsepower - to get yourself some footing on the subject.

The best person to answer your question is the guy who programmed your chips. He knows how much ignition advance you're running which has the biggest impact (in addtion to octane) on how much boost you can run. All of these considerations are aside from the issue of up to what pressure ratio a K26 is reasonably efficient, and that's a real issue.

Charlotte944

Detonation.

By upping the boost you are also raising the effective compression ratio, 'cause you're squeezing more stuff into the same sized hole.

Detonation is a function of the fuel octane, the compression ratio, the temperature of the compressed gas, and a bunch of other stuff.

By upping the boost and leaving the octane alone you are heading for the "knock point" of the fuel. Good way to blow a motor.

HIGHBOOST

Your timing will need to be retarded slightly as well

pk951

From what I have seen you should be able to run up to 20psi on 93 octane without a problem.

I would not run 20-psi on 93 octane.

porshhhh951

okay I will share my imput since I am one of the few guys on this board that runs that kind of boost on a 26/6. For the record I do not recomend you run any more than 18psi unless you are tuned for it(meaning timing/fuel). There is a performance benefit to running more boost just not hp. Our stock tiny turbo's really stop making hp at 18psi.....turning it up to 19 or 20 at that point wont yield ANY MORE hp. BUT, you gain considerable tq. And tq is a huge performance factor 0-120mph.

Now I read your on stock injectors!!!!!!! 16psi is impossible on a completely stock fuel system so I assume you have upped the fuel pressure somehow either with a regulator or a larger pump or something. Dont dial up anything until you buy yourself a set of injectors. You would be asking for trouble. You need the fuel period! buy some 55's and get yourself a new set of programed 18psi chips and call it a day. For most people this is enough.

The only reason I run and get the absolute most outta my tiny stock turbo is because I like power and tq and I figure why not find out what the stock turbo can do while I am trying to decide on a upgrade(vitesse needs to have a sale.lol)

Oh and for anyone who doesnt think you can run 20psi on 93octane....ummm I guess you just never have. My car has seen 20psi on nothing but pump gas since june of 03. It's been quite awhile and I think I if I was going to have any real problems....they would have come by now. The problem is most people arent properly tuned for their application. If you are going to run that kind of boost you need to make sure your properly tuned for it. Oh and during the days here in the summer where the humidity is crazy along with 100degrees....I dont think all the retarded timming in the world would help keep you from detionation on 20psi and 93 octane.....at that point if you wish to run 20psi on pump gas even in those extreme conditions water injection is the way to go.


If you still dont believe the performance benefits of running higher boost levels than 16psi...you can check my sig. My 93 octane dyno #'s are in there.....and they are corrected.

Evan70

Thanks John, that helps me out. The main thing I would like to do is actually get to 18psi on the stock turbo. At this point I really don't feel safe going past 16-16.5psi since I'm hitting 13:1 at that level. And yes, I've got a 3 bar regulator. Whose chips are you running for your 20psi setup?

porshhhh951

oh 3.0fpr is how you are doing it then. Cause when I was stock I was hitting fuel cut at 14psi.

Kokeln stage 2 base wth a dave lindsey reburn and tune and then some fine tuning with powerperfect and pro-m down the road later.

For the record I have been thinking about calling up john at vitesse and having him send some new custom chips over to me for my application while I sit and ponder about turbo upgrades. He knows alot more about timing curves and tuning than I ever will.

hosrom_951

I got knock at 17psi on pump gas with certain chips IIRC