There are numerous things that effect how much boost you can run safely on pump gas (91-93). Cylinder head design, dynamic compression, compressor efficiency, intercooler efficiency, charge air temperature, exhaust manifold backpressure, ignition timing, ect.. the list goes on. The things we are interested in are items that we can easily change on the car and make it less detonation prone. I already ran the limit on our EVO VII and I'd say you can safely run 18psi on an otherwise stock car (93 octane). Want to run more boost? make it easier for the air to get in and out of the engine and at the same time you'll be dropping the charge air temperature. Remember just because your boost gauge says 19psi doesn't mean that the turbo is putting out 19psi at the compressor outlet, usually it's much higher. Along the whole intake tract you have flow losses that account for a pressure drop (for example an intercooler itself is a restriction) and if you minimize these losses the turbo will have lower compressor outlet pressures (for the same intake manifold pressure) and temperatures. A turbo is nothing more than an centrifugal compressor and whenever you compress air you are putting work (energy) into the air which results in the temperature rise. A more efficient compressor wheel will put less work (energy) into the air and thus result in lower outlet temperatures and at the same time moving a larger mass of air. For those interested in reading compressor maps or an explenation of pressure ratio's (absolute & relative pressures) I wrote a little article a while ago and can be found here.

http://www.vfaq.com/mods/Turbo-compressor-maps.html

For those really interested in turbochargers look up these two books on amazon.com - Turbochargers by Hugh McInnes and Maximum Boost by Corky Bell it's pretty interesting reading.

-Martin

 

Blah blah. I don't care if people blow there motors. The guy originally said "23psi on pump cannot be done". He was so emphatic about it. He is wrong regardless of what the "average person" can/will do. Now that you guys have been proven wrong you are throwing in all these qualifiers:

"well when I said that I was talking about just the EVO"
"well when I said that it was pertaining to the average person"

Blah blah. Whatever. He made a statement that was wrong. He got called on it. End of story.

Why is everyone on this site so unwilling to listen? Do you not realize that some of us have been doing this forever with the 4G63? Do you think we say this stuff for our health? Do you think we are purposely trying to mislead you? What is it? Lay it out for me.

 

Anyone with the willingness to learn to tune their cars can do what I’ve done. As for daily driven and reliable; I’ve not run 100,000 miles this way, but so far so good. It's a daily driven car and it is very reliable (other than the crapbox transmission Subaru put in it). I want to warn you against making blanket statements such as, "you can't do x,y, or z," because someone will come along and prove you wrong.

-Nathan

 

No matter how crazy stuff sounds someone somewhere has done it. And it was probably a guy with a DSM and he was probably happy as a pig in **** when he was doing it.

 

you know what.. i dont care anymore.. for those evo8 owners with stock cars who decide to run crazy high boost because you have read it on the boards go for it, remeber it came straight out of the mouth from nathan of turboxs..

the point of my posts was to simply help the people who dont know much about turbo engines from thinking they can run some absurd amount of boost w/ their stock cars on pump gas and have a healthy and reliable ride.. not what a professional tuner and someone who has the funds and ***** to take the loss when something breaks..

flame on..
--bobby

 

Bobby,
I think you may have a reading comprehension problem. I never stated that a stock EVO 8 could run 26psi on pump gas. I stated that you should not make blanket statements just because you can't do something.

That's right Nathan@turboxs said the above. I get tired of all the blanket statements thrown around in the WRX world; I think WRX guys should avoid polluting the EVO world with the same sort of unfounded crap. If I had a dollar for every time I've been told I "can't" do something that I later proved could be done, I'd be a very rich man. Unfortunately life isn't like this so I have to ***** myself out for weekend dyno work to pay the bills.

You know what else I get tired of in the WRX world? People, who take what tuners say (including myself) as fact, who quote it on internet boards with no understanding of the actual quote, and with no idea of the context of the discussion.

 

ditto.. read my last post again.. i may have made a blanket statement in my first post but i have explained my reasoning for doing so.. you dont seem to understand that.. and once again many people could care less what a professional tuner can do with their own car.. its what they will be able to do with theirs safely..
--bobby

 

The blanket statement part is what I don't understand or care to. Let me explain...
ie: If Joe Q. Public can't actually read my posts where I state more efficient turbo and big fmic, then it's his problem. All I was saying is that your blanket statement was kind of wrong and therefore bad info.
Assuming there is a bunch of dummies here might not the best thing to post either.

Post good info and then let the good happen. If you dumb down the info for the one or two people who shouldn't own an evo8 then the real enthusiasts get hurt and run slow. That's bad.

You guys want the EVO8 to run fast? Then take some lessons from DSM guys. Martin made some excellent points above.

 

That's what I thought. I just wanted to make sure we weren't talking apples and oranges.

When is your timing advance only 10 degrees?!! That sucks! Any mods yet? Got exhaust?!

I'm already thinking you're too rich up top. Are you hiding knock with fuel and that's why she goes really rich? Or is that just stock outputs?

 

Timing set that low will tend to raise your EGTs, and your power really suffers. Generally, I aim for around 19 degrees advance total at WOT on pump gas at high RPMs. Remember that timing advance has to go up as the RPMs increase. This is because there is less time for the combustion to occur. But you still want to give the combustion adequate time to hit max pressure just after TDC. So you have to advance the timing as RPMs increase. Mitsubishi ECUs tend to do this on their own.

On race fuel, I aim for around 23 degrees of advance.

 

Hey claud you have a VTA BOV?? why did you change to MAP.. sorry i'm not a turbo guy.. i'm car retarded also