387 rwhp on pretty much a stock GT motor

[Danglerb]

The whole story is on rennlist
http://forums.rennlist.com/rennforums/showthread.php?t=466038

Summary
DennisK had his motor seize last year on the track, and Bill Ball and Jim Morton joined in to help him build a new motor. 91 GT rotating assembly, I think S4 block, heads, and intake without porting. Mods are base circle reduced cams from Elgin with more lift and duration, Devek II headers, X pipe, and racing mufflers, and a full Sharktune on the dyno.

Its a good 10% more rwhp than I would have guessed possible from the combination, and with a different exhaust (adding cats I assume) it passed Cal smog.

[DanielDudley]

That is hot. Didn't Porken make some absurdly high HP on a stock 86.5 recently ?

It makes me itch to replace the wimpy stock exhaust on my 85. The car has headers and cat delete, but I hear that a true dual is good for 25 HP.

[N2O-SHARK]

More than 10% more than I would have expected.

Very cool. Then again.. lots of Dyno operators bump the correction factor with out letting you know, figuring you'll always use the dyno service that gives you the highest numbers.

I have actually found my G-tech more consistant then the 3 dyno's I have used locally at Dyno days. Funny how dyno numbers go up through out the day as folks start *****ing about low numbers early on.. PLus the G-tech is real world, real road, not hood up on rollers with a HUGE fan blowing on the motor..

Still very impressive.

[BrendanC]

Its very realistic. Higher compression, proper tuning, all new parts, improved cams, etc.

[N2O-SHARK]

I hope I get the same gains from my cams which are even more aggressive.

[Danglerb]

GT motor is factory rated at 335 "crank" hp isn't it? Which is about 285 rwhp. Its a big step to 387 rwhp, like a 33% gain.

Stock heads, no porting, stock intake, throttle, airbox and filter.

Headers rarely have more than a few percent.

The merge pipe and high flow exhaust we know are good for around 30 or so hp.

My impression was gains from a reduced circle small enough not to mess up the lifter oiling, where not that big?

Still Mustang dyno usually has solid numbers, the track will tell all though.

Whats Kibort getting out of his stroker?

[BrendanC]

Not even remotley what he should with just a bit of work.

[rhjames]

nice numbers....and why not.


it is an interesting thread, with many questions about this and that which could be answered if someone would just take the time to do the testing.

However------

As Jim Bailey put it, so many things are done at the same time, there is no base line to determine where the gains are actually produced. I have read so many dyno numbers with no base line to go by, it makes my head spin (I added /changed five items and got 50 more hp.....).


If one was to do in-depth research (in my mind----item by item testing), then publish the results for folks to review, then we as consumers would have a better idea of what to spend our money/labor on. Even then, someone would argue that this dyno or that dyno doesn't reflect true results........We've seen it before, we'll see it again.


Carry on------





--Russ

[N2O-SHARK]

Even testing one by one, you won't get the whole picture, though it may help let folks know where to start.

Add headers and you get 20hp more, take headers off and add cams and you get 30HP. You would think both would then geive you 50hp. However together you may get 60hp. ie the right combination of parts will yield a total greater than the sum of the individual parts. I think Spok said that once on Star Trek once.

[jmorton]

As a follow up...

We agree that "the track will tell all"...

Dennis is taking the car to TH on 12/1. We are both excited and cautious as the day will be a real world test of all the work.

We created a test port in the oil galley and plan to log pressure during this first track day. We're curious to learn how stable the oil pressure will be while in the sweeper turns that proved troublesome in the past.

We'll post what's learned after 12/1.

Regards

[Barbapapa]

Hi Jim.
Congratulations!
It will be interesting to hear about the oiling. I tried things for a wet sump but still saw pressure drops. I have a 79 with a pan spacer and louvered windage plates around the crank. For the sump I use an early screen that has been opened up, the idea is to keep oil from sloshing out of the sump.
Those mods did make a difference but I can still see the pressure drop on some turns, it's a racer on slicks.

[Normy]

What about this:

Instead of a thread where people attack each other, why not post results with full backups.

Backup your post with a dyno post, and then describe very carefully the conditions that existed when the dyno pull took place.

-There is a thing known as density altitude. If you are in the mountains, or it is a warm day, then dyno readings will naturally be lower than they should be.

The International Standard Atmosphere:

temp: 59F/15C

pressure: 29.92 in of Hg/1013.2 millibars

-You lose one inch of pressure per thousand feet, which means that at Dave and Jeanie's shop in Western North Carolina [2200 feet MSL], means that you would lose about two inches of pressure. Since you lose 1/2 pound of atmospheric pressure per thousand feet, you would then need one pound of turbo or supercharger boost to make Dave's red '85 S2 perform the same as my graphite '85 S2 does just out of my garage, at 9 feet MSL in Fort Lauderdale.

Temperature changes that quite a bit! If it is COLD in western North Carolina, then Dave's red car just might keep up with mine. I have an electronic calculator that calculates "density altitutude", something that we use in aviation to determine whether or not we can take off from runways. Some are rather short, and it is probably in our interest to know this before we aim the 727 down the center stripe-

A dyno post without corresponding conditions does NOTHING. People sometimes take their cars to sea level, and record the dyno readings on a cold day. Those readings are a huge joke! I can tell you that my car on a 60F/ 16C day would DESTROY the same car on a 90F/32C day! I suspect that it is close to a full SECOND difference in a quarter mile!

That's my car, a peaky S2. The S4/GT/GTS cars probably have less of this effect, since they have more torque.

N!

[N2O-SHARK]

The key will be in repeatable results. I think it's amazing they got those numbers with just a slight cam grind and free flowing exhuast. AS fort the sharktuner, did Porsche miss the mark that much? With almost 8 years after the S4 came out, you'd think they would have done better than just increasing displacement.

Almost makes me want an S4..almost.

[Danglerb]

A basic problem is that chassis dyno's rarely have any kind of calibration, and generally were never intended to measure absolute values, just to show changes in tuning. Most do have correction for temp, barometric pressure and humidity, but only for run to run consistency on the same dyno.

Dyno results are in the main thread, timeslips are what I am curious about.

More than about 310 rwhp is extraordinary for a 5.0L motor, and usually reflects intake and head work as well as cam and exhaust. 350 RWHP under 7k rpm and something very special is going on. 387 rwhp and my first thought is measurement error, or estimated crank hp instead of rwhp.

I hope its all golden because I would love that kind of power from those simple changes.

No point hashing over it too much, just see how it does on the track.

[rhjames]

Originally Posted by N2O-SHARK

Even testing one by one, you won't get the whole picture, though it may help let folks know where to start.

you are quite right, but the questions on the thread were along those lines.


matching components for the best tune sometimes will leave shaking your head asking why.......?





--Russ

[Danglerb]

Generally you want intake, exhaust, heads, and cam all to suit each other. More isn't going to flow out the exhaust unless more goes in the intake etc.

[m21sniper]

Too much going in the intake and not enough going out of the exhaust is just as bad.

[Danglerb]

Originally Posted by m21sniper

Too much going in the intake and not enough going out of the exhaust is just as bad.

I'm not so sure, it doesn't seem like a symetrical situation. The intake flow at best NA has 14 psi pushing in the air, and as the cylinder fills the pressure drops to almost nothing. Exhaust starts with hundreds of psi pushing out and doesn't drop below 14 psi until the cylinder is nearly empty. Some kind of balance is obvious, exactly what is best perhaps less obvious.

[m21sniper]

More air coming in than going out creates backpressure. Back pressure is wery bad if you're trying to build max power. Especially for a turbo car. Back pressure= turbo spool up lag. Some amount of it can be beneficial for a NA street car, as backpressure also aids in low end grunt.