Guest

So I finally got dyno results. I can already hear the opinions and criticisms, so... speak but like in the Conseco commercial "I cant hear you."

Anyway here's the deal. I decided to do something totally unusual, and siamese part of the runner lengths in the base, more specifically the 2 that are next to one another. I cut down 5" into the base totally taking out the wall between the 2 runners aside from areas the casting prohibited me from cutting. An aftermarket base like the Edelbrock or Accel would allow a completely oval hole rather than the silly sunglasses style I have now. I guess you should see what it looks like first. I only have these 2 pics. I took some of the manifold after I took it off the TA to put on the Grand Prix and... damn cameras... the stupid film wasnt in right and didnt advance . So for now, these are the only 2 I have

Doesnt look like much does it? At least not on this side. As you can see, I did port the openings going to the head side. These pics were taken sometime inbetween start and finish, so there was more grinding done after these were taken.

This shows more what I did. I rounded the area between the 2 runners better than what you see here, and did some more grinding around the entries to take out the stupid rolled edge that there is stock.

Ok, what am I comparing here? Heres the deal:
Start;
Stock 88TPI intake from the TB to the base, totally untouched cept for some dents in the runners I attempted to fix.
Finish;
85 TPI base, siamesed. The rest, including everything else on the engine (that includes timing, fuel, etc) are the same as the first test.

Results?
Start;
237.0hp@4900, 266.5tq@3500. Pathetic, especially for what this car should be putting out. Came across some problems on the dyno run that I did not know of, so I will be fixing those. No, I didnt fix them yet.
Finish;
256.8hp@4860, 281.7tq@4000
Had a slight problem with this one. The first run, he let off at 4860 because it felt like it lost power as he said... So we made another run, and I heard a rocker arm clicking So I had him abort the run and didnt make a 3rd one.
We were checking out the graphs for a while, and it is readily apparent we never made it to the hp peak. I dont know how much I would have picked up if we had. The tq from where it was started to the end was never less than with the stock base either.

SOTP impressions;
The car doesnt feel as asthmatic as it did before. I didnt mess with a damn thing that has to do with the tranny (the TB never came off the plenum either, nor did the bracket) and for some reason the shift point sailed up into la-la land. Why? Dunno. It used to shift at about 6300. My dad drove the car first, and it was headed past about 6800 and went to around 7000 by the time he let off so it would shift. I didnt setup this valvetrain for more than 6000 yet, I need a rev-kit before I want to risk that one. It picked up alot of rpm here. It definitely has more power from what I can tell. The dyno graphs show it as well. Could this gain be accomplished with just porting the base? I dont know, I would assume that from what I hear you could pick up quite a bit from porting. Keep in mind I did not tune the car at all. It has a loose rocker. Its running lean (pings now past 4000). The timing could probably use to be messed with as well. I didnt get as good of results as I had hoped (I was honestly looking for 30HP) but then again the second test was far from ideal unfortunately.

Is this for you? Good question. I had the manifold on my TA first with the old tired, cracked block 86 engine with a small cam, and it definitely helped. I then replaced the POS 86 engine with a 91, has the 'good' cam and threw the manifold on there. It felt good, felt cam limited not manifold limited. Now its back to a stock base, and it doesnt feel any faster.. or slower for that matter. I am going to gtech it later today (I know, but its the same gtech, same road, and I have lots of previous runs) and see what sorta times it turns now. My initial instinct would be to say if your engine is stock or has a mild cam, dont even think about it. For those of us with engines that want and need higher RPM's I think its just what the doctor ordered. The engine in the GP I had taken up to 7000 before, but even though it pulled pretty damn good for a TPI, it struggled a little. It doesnt struggle anymore. It feels much better, and from that alone I feel it was worth it and I am leaving it this way. Only thing I might do is clean it up some more, maybe take more of the wall out and see what happens.

I suppose I should tell you what engine I have in the Grand Prix. Its an 88 block, 86 vette aluminum heads (home ported) stock injectors, had a stock intake, stock MAF, stupid exhaust, headers, SLP cam (224/232 .497/.517), and 10.3 compression.

Nows your chance... post whatever you are thinking.

Oh yea... I have graphs but they are not scanned yet. Ill post those soon as I can get it done.

[This message has been edited by madmax (edited February 21, 2001).]

Dan91Z

hmm.... I'm thinking about buying another base, plenum, and throttle body from the junk yard, and get a set of used after market runners and trying what you are doing.. looks to be a good way to get power


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My `91 Z28 Convertible

Red Devil

Max, I had done this to an Edel baseplate and used the SLP runners, hogged those out all the way and matched the plenum. I had a 52mm TB on it with AFPR and SVO inj. In SOTP feel there was great difference, however, I also wrecked the car about a week after the mods were done (still have some nasty pics of the wrecked car)! I was in the hospital for about two weeks, and I couldn't save the stuff (and needless to say my parents were quite glad to be rid of it). When all of it was done, I did have a tad harder time spinning the tires, but at about that time I swapped tires so I have nothing definitive. My MPG did go down a tad but only about 2 MPG, so it was not too bad. I had tried it on a stock manifold, but I kinda destroyed it trying (my first encounter with a die grinder). Never tried it again, it's a PITA and my son always tries to steal the die grinder from me so I just stuck with sheetmetal manifolds and aftermerket parts. Well that and all my car buddies convinced me that it was crap and a waste of time. Stupid me, but I had no numbers to back me up, and at the time women were a bigger attractant than knowledge. One thing I did do to kill some of the turbulence at the end of the runner was to rifle the port a bit and knife edge the split. It is a great idea, but I think I could have had a better time if I swapped cams and a custom PROM would have been great, but they were not too popular then. All I had were warmed over heads and my car was a bit tired too. Maybe I should try another one.
So how many hours you have in the manifold now??

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"Only in Britain could it be thought a defect to be “too clever by half.” The probability is that too many people are too stupid by three-quarters."

John Major

Guest

Actually I dont have all that many hours in it, I used a mill and a real nice cutting bit
I think I have about 8-10 hours in it as a guess. I didnt molest the runners yet, but thats the plan. Right now I just have the stock runners and stock gaskets on there. I'm sure theres a real nice eddy there, but I'm not really concerned about it right now.
I havent decided if I am going to get another TPI and do the next step with that, or cut this one up some more, or maybe slice+dice my 86 intake that came off the TA. Seeing as how the TA has a 91 motor and 88 intake... I dont think it needs the 86 intake anymore Basically I am going to attempt to shorten the runner length using stock parts, selective cutting, lots of welding, and a few prayers.

Vader

Max,

What you did is to effectively change the long runners into a short, "detuned" runners, much like what was done on the LT1s and in the MiniRam. Although they went a bit farther and eliminated all the extra length of runners entirely. Imagine what a regular MiniRam would do now that you've experienced the effect.

Your high end flow should be a lot better if for no other reason than less wall turbulence loss and larger runners, and should also not be fighting the stock pulse tuning of the long TPI runners.

However, the low end torque is proabably notably lower than it was. It sounds as if Red Devil's experience would confirm that to some extent, and your dyno run peak torque is now at a higher RPM. For someone that doesn't mind losing the benefits of the additional low-torque of the TPI system for a lot better upper RPM flow, the change wouldn't be a bad idea - a kind of home-grown MiniRam. After making the runners a little more regular in shape, your numbers at the top end should get even better. If you can change the cam to a higher-RPM flow design you'll get the most from this change. Now just get some more fuel to it at WOT and start working on the exhaust - and don't forget the extra valve springs. You might even want stud gordles if you are planning on frequent 7,000 RPM jaunts.

Not to belabor a point, but this is all through a stock 48mm TB and stock MAF, am I correct? And some people say that the stock MAF is too restrictive. Until you do something like this, the benefits of a larger TB and MAF housing aren't very impressive. You are at a point where you might see some benefits.

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Later,
Vader
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"No matter how hard you try you can't stop us now..."
Adobe Acrobat Reader 4.0

Vader

Max,

Incidentally, by your current numbers, I'm projecting a net of 271.6HP peak and that's at the rear wheels, running lean (your current running configuration with a reliable valve train).

It looks like you're already very close to 300HP at the crank, and if you solve the fuel and timing problems, the 330HP mark is not unreasonable. It's pretty impressive what can be done with adequate intake flow, isn't it?

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Later,
Vader
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"No matter how hard you try you can't stop us now..."
Adobe Acrobat Reader 4.0

R.O.B.

What was your vacuum like? Did it change at all?

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Rob
'86 TA 305 TPI
Gutted MAF
Ported Plenum
TB Bypass

Guest

Vader, the guy at the dyno shop was playing around on the computer and came up with about the same number, I think he said it should have hit about 270. I can deal with that for the time being. I dont have stud girdles in the plans (stupid centerbolt heads) but its making me wonder now with how much it wants to pull to rediculous RPM's. At least I know the lower end can handle it
And yes, thats with a stock TB and MAF, no screens removed, no air foil.
Rob, I knew there was something else I wanted to check out. I think its lower at idle now if I remember what it was correctly, but I dont know what its doing at WOT, never checked that before.

Torque... well at 3200rpm I now have 260, and before at 3200 I had 248. I dont have numbers for anything below that, but SOTP I would say its less at some point for sure. Past 3000 its more all the way up. At the previous peak it was 266, now its 272@3500. At 4000 before it was 261, now its 282.

Dont have the stuff scanned yet, dont know when I will. Been a really frustrating week and Im not much in a mood to break out the scanner so you will just have to take my word for now. I also want to make an approximate graph in excel comparing the 2 best runs, it will make it much easier to see that way.

Guest

BTT

Heres the real deal, the comparison between the two:



Take a close look at 4800rpm+

Heres the actual dyno sheets:
http://home.earthlink.net/~wtomfoster/Dynorun2.jpg
http://home.earthlink.net/~wtomfoster/Dynorun4.jpg