toddk911

Yea, and??? LOL!!

User 41221

Yeah, I tried that and it worked really really well, but I did have a problem that I couldn't solve, maybe you have the answer. I can only get about 150' of extension cord before I run out of cord and have to stop. Where do you find the really long ones?

Chris White

Keep in mind that flow benches - like dynos - cannot be compared to each other unless all parameters are equal - including barometric pressure!
Stock – intake 190cfm, exhaust – 150cfm
Highly Modified - intake 250cfm, exhaust – 220cfm (this was a $4k head job!)

BTW – velocity is as important as flow….

Chris White

Geez, do I have to give out all the shop secrets?
Honda generator in the back seat.

Chris White

Higher octane allows you to run more aggressive timing. Unless you have a way to modify your timing you will not get more power (at the same boost) with higher octane.

You ‘may’ be able to run higher boost with a lowered chance of detonation – then its back to how much HP per lb of boost….

333pg333

While those numbers can't compare to a 16v head, that is still a vast % improvement. If the stock head was designed for low to midrange tq, what was that head built for? Mid to high I'm guessing? What sort of cam went into it. How well does it perform it's nominated task overall?

George D

SirLapsalot....gross. LOL....anyway here goes.

As someone stated in this thread, there is some voodoo going on when it comes to head design. I'm not an engineer, nor am I a very good wrencher. I have other skills, so my point should be taken as second hand knowledge coming from knowledgeable sources. I remember car stats, enjoy auto knowledge, and love driving bad *** rides. I pay others to do most difficult work on my cars, and have been known to offer free pizza, beer, and booze for help from listers with my cars at my place.

The issue I had with my EVO was it had little feeling of TQ from the drivers seat. The dyno showed tq, but you didn't feel it like a well setup 951, big v8 or, my favorite tq motor, the Duramax Turbo Diesel. This is why dyno numbers may be fun, but you HAVE to drive the car to know if the parts you just spent a wad of money on actually made your car faster. A machined EVO head should flow 270 CFM at .500 lift. The Voodoo comes into play because you have to consider flow rates at low, mid, and high lift. You also have to realize that Mitsubishi spent millions in R&D on their 2.0 turbo motor and blew 100's of motors before they got close to a final product. Porsche did the same thing with our motors many years ago with the intention of finally producing a turbo inline four that felt like a much larger motor. A EVO motor feels like a turbo four with little tq. A 951 motor with a properly sized turbo feels like a much larger motor and that's because it was designed for good mid range power.

Why can a 2.0 EVO inline four handle 30lbs of boost on 91 fuel with just a few bolt on mods and a flash? I don't know, and most tuners don't either. I've been told by good Porsche engine builders a 951 motor with supporting mods should not exceed 17 to 18 lbs boost on 91 fuel? Believe me, I've asked why. Garrity tells me it's partially the design of the 8v head, cam, and all else that went into the design of the 951 motor. A 2.7 N/A ported big valve heas will probably flow as well as the EVO head when open. There is much more going on when you bolt everything together and start exploding fuel and air. Voodoo.

The EVO motors came from the factory running 21psi and would do this with 89fuel if the owner was dumb enough to add low octane pump. These cars, as stock had a good warranty and had to perform with a bad tank of fuel with NO issues. 30psi is within the operating range of the EVO motors. Remember our stock boost was rated at .75 bar or 1.75 bar on the factory guage, or 10.88psi. We see 17-18psi on many modded 951 cars running 91 fuel, and some have theirs set even higher with no (yet) issues.

There isn't really an answer, other than to state that the Porsche engineers wanted a turbo four that had great mid range power and designed everything around this goal. These motors are tq producers with great mid range as compared to something like the BMW V10 with a redline of 8250.

Someone told me that TQ wins races and HP sells cars. I do love the shove in my back when my car is on boost. No other car feels like it.

Scott H

When tuning how do you know how much advance is "enough?" I've seen people say "advance it until you get knock then retard it a little," which seems kind of stupid to me. Is it one of those things that's ideally done on a dyno to see if more advance actually produces an increase in power?

Chris White

The first 8v head I did with these kind of flow numbers was used in the engine I built quite a while ago that ended up on Special Tools dyno with a 440rwhp @ around 15psi. That engine had some serious midrange torque. It was not built to be a high rpm dyno queen but it still put out some good numbers at higher rpm. The latest version is over in Europe with more displacement and a dry sump system. That one could be the best midrange torque motor yet – its being finished and should be on line when the snow melts this spring.

I like to build the 8v engiens with midrange torque in mind. The head, intake, cams and headers are all designed for that in mind.
If you look at the dyno charts of the high power Evos you will see some pretty crappy mid range torque numbers. Torque is a much better indicator of how efficient the design is – it also means that you are closer to detonation sine you are closer to maximizing the output. The fact that some other engines can run more boost at the same rpm does not always mean that they are better – they may be operating well outside the efficiency range and the boost is just making up for that.

Torque curves do not lie…hp numbers can be misleading!

Here is an evo dyno chart that I found with a quick search – the torque curve sucks. One peak and then it rolls off – badly match parts that run 30 psi because they are running inefficiently. I am not an evo expert – but if that’s a 2.0 liter engine running 30 psi and it makes 386 ft lb of torque ‘peak’. My old 2.5 made 350 torque over 3k rpm @ 15 psi.
25% more displacement but running 50% less boost….and the peak torque numbers were in the same ballpark. By 6500 rpm I had 15% more torque.

Here is a little bench racing math –
Raise the Evo torque by 25% to equalize displacement – 475 ft lbs
Decrease the out put by 67% to equalize pressure (3 bar absolute vs 2 bar) – 317 ft lbs
So if we equalize the playing field the comparison is 317 to 350 – in favor of the 951. That tells me which one is running more efficiently!

Chris White

I think he may mean laps on the track....not the other kind!

George D

I was waiting for someone to get my attempt at humor.

SirLapsalot

Chris and George,
Thank you for the great information. I'm loving hearing from you guys and seeing those dyno sheets to go with the numbers. Great stuff.

Oh and I've been studying hard for finals and my brain is kind of toast right now so maybe that's why I don't get it buuuuut.....what other kind of lapping would I be doing that is gross?

Chris White

it involves a lot of sticky single dollar bills....

George D

This is what you don't want on a 951 in terms of a power curve. This turbo is just TOO big. It's the Lindsey Super 75. I'm NOT saying it's a bad turbo, and this power curve might be the **** for the right guy, just not what I wanted in a street/DE/track setup. This car was very laggy out of the corners. The EVO's would catch me in the corners only to see my *** from 100+ yards on the back straight at Arroyo Seco. The lag sucked, but once on boost you did have a grin.

Chris White

The other way to look at it is that the turbo was not too big – its that the engine was too small! Swap the 2.5 engine for a 3.0 and that turbo would have been pretty good!