Speed-Talk is running on www.Speed-Talk.com

IMPORTANT: Update your bookmarks to https://www.speed-talk.com/forum/
(Right-click the URL and select "Bookmark this link")

Dyno result for the risky business Porsche

General engine tech -- Drag Racing to Circle Track

Moderator: Team

Post Reply
User avatar
ptuomov
HotPass
HotPass
Posts: 3036
Joined: Fri Aug 07, 2009 3:52 am
Location:

Dyno result for the risky business Porsche

Post by ptuomov »

Here's a recent dyno result.

The base car is '87 Porsche 928 S4 with 32V 5.0L V8 that produced 318 crank hp from the factory. These cars are out of favor, and you can pick up one from ebay pretty cheaply (for example http://cgi.ebay.com/ebaymotors/1987-Por ... 721wt_1026)

Mine has been hot rodded a bit. There's a twin turbo system installed, new dual 3" exhaust, a higher-rated clutch, bigger fuel pumps and pressure lines, and eboost2 boost controlled. What is more interesting that the entire engine from the throttle body to exhaust ports is completely stock. Stock intake, stock cams, stock throttle body, stock valves, stock pistons, stock rods, stock crankshaft, stock transmission, etc.

Here's the dyno graph. The car made 711 hp at the rear axle (Dynapack hub dyno):
Kuhn Performance 928s.JPG
Here's a video from the test:
http://www.youtube.com/watch?feature=pl ... xn-LxwsrnU


Here's a photo of the engine compartment:
Newton-20121111-00048.jpg
You do not have the required permissions to view the files attached to this post.
Paradigms often shift without the clutch -- https://www.youtube.com/watch?v=cxn-LxwsrnU
https://www.instagram.com/ptuomov/
Put Search Keywords Here
POS Dakota
Member
Member
Posts: 147
Joined: Sun Aug 22, 2010 10:53 pm
Location:

Re: Dyno result for the risky business Porsche

Post by POS Dakota »

The car looks to be in really good condition. nice numbers.
xanadu
Pro
Pro
Posts: 329
Joined: Thu Aug 28, 2008 5:41 am
Location: Brisbane Australia

Re: Dyno result for the risky business Porsche

Post by xanadu »

Cool project! Should be a lot of fun. Well done
englertracing
Guru
Guru
Posts: 1375
Joined: Thu Sep 29, 2011 8:55 am
Location:

Re: Dyno result for the risky business Porsche

Post by englertracing »

That's good work.
I by far prefer the look of the 944 tho.
gmrocket
HotPass
HotPass
Posts: 7606
Joined: Wed Nov 12, 2008 6:40 pm
Location: Grimsby Ontario

Re: Dyno result for the risky business Porsche

Post by gmrocket »

nice. anyone know how to make my 2.5 86 944 a little quicker :oops:
user-9613590

Re: Dyno result for the risky business Porsche

Post by user-9613590 »

gmrocket;once I did a quickie job on one of those.Mostly seat work and some in port.Flow increased about 8% and voila! same amount of power increase in dyno :D
eikoor
Pro
Pro
Posts: 235
Joined: Wed Apr 03, 2013 2:06 pm
Location:

Re: Dyno result for the risky business Porsche

Post by eikoor »

I've always liked the 928 and wanted one but didn't know how dependable they were, any idea how long it will live making this kind of power?
Is your auto or stick?
User avatar
900HP
Guru
Guru
Posts: 1984
Joined: Sun Jul 04, 2010 6:56 pm
Location: Fargo, North Dakota

Re: Dyno result for the risky business Porsche

Post by 900HP »

I've always loved the 928's. I think they are the neatest Porsches ever (with maybe the exception of the GT3's -- they are cool too). Awesome job, that thing is cool!
Throttle's Performance
(701)893-5010
https://www.facebook.com/pages/Throttle ... 1996281602
User avatar
ptuomov
HotPass
HotPass
Posts: 3036
Joined: Fri Aug 07, 2009 3:52 am
Location:

Re: Dyno result for the risky business Porsche

Post by ptuomov »

Thanks for the kind comments. The kit and most of the work was done by John Kuhn of http://www.kuhnperformance.com/.

I really like the 928 for its looks and it because it was the second car I ever owned. V8 never hurt anyone either...

People who like the 944 better usually like them better for their nimble handling, but not for looks. That said, no arguing about tastes.

The 944 engine was designed by taking 1/2 of the 928 engine. Half glass full looking at it is to say 944 engine is as good as 928 engine. Half glass empty looking at it, it's only half as good. ;-)

My car is a five speed. The 928's are very expensive to maintain (especially if you pay for labor) but also very reliable if maintained properly.

We don't know how long this stock engine will live at these power levels. We've been trying to break it in an interesting way for probably about 50 dyno sessions and we have failed. The '87 engine design was turbo protected and the factory had a test mule in Germany running at 750 chp for a while. All in all, we have no idea what the true limits of the engine are.

There are three weak spots for daily driver / registered track car dual duty vehicle: (1) If the manual transmission overheats on slicks, it breaks. No similar problems with the auto. (2) On slicks, the g-forces cause engine oiling problems. (3) Engine cooling is on the edge, especially with the A/C on.
Paradigms often shift without the clutch -- https://www.youtube.com/watch?v=cxn-LxwsrnU
https://www.instagram.com/ptuomov/
Put Search Keywords Here
englertracing
Guru
Guru
Posts: 1375
Joined: Thu Sep 29, 2011 8:55 am
Location:

Re: Dyno result for the risky business Porsche

Post by englertracing »

900HP wrote:I've always loved the 928's. I think they are the neatest Porsches ever (with maybe the exception of the GT3's -- they are cool too). Awesome job, that thing is cool!

Neatest?
You must have never seen a 904, 917, or the carrera gt!
User avatar
900HP
Guru
Guru
Posts: 1984
Joined: Sun Jul 04, 2010 6:56 pm
Location: Fargo, North Dakota

Re: Dyno result for the risky business Porsche

Post by 900HP »

englertracing wrote:
900HP wrote:I've always loved the 928's. I think they are the neatest Porsches ever (with maybe the exception of the GT3's -- they are cool too). Awesome job, that thing is cool!

Neatest?
You must have never seen a 904, 917, or the carrera gt!

I know exactly what a 917 is but they are not street legal. I have driven a carrera gt and it's a bad-ass car but absolutely no character. Throttle response is completely wicked but in all honesty the GT3's really do it for me. They just SOUND so good. If I ever came into big money I would buy one just to drive around and listen to. The last GT3 I drove was a 2012 GT3RS and it's just plain SICK! I love that car, even better than the Turbo S I also drove.

HOWEVER, I have ALWAYS had a soft spot for the 928 S4. I just love them and I can't tell you why, I just do. Great Job with the 928, I love it!
Throttle's Performance
(701)893-5010
https://www.facebook.com/pages/Throttle ... 1996281602
User avatar
ptuomov
HotPass
HotPass
Posts: 3036
Joined: Fri Aug 07, 2009 3:52 am
Location:

Re: Dyno result for the risky business Porsche

Post by ptuomov »

900HP wrote: HOWEVER, I have ALWAYS had a soft spot for the 928 S4. I just love them and I can't tell you why, I just do.
Me too, I like the looks.

It's a bit sluggish as stock compared to new cars, but the turbos help keeping up with new Audis and Acuras... ;-)

By the way, there's more power in the stock engine to be found.

Notice how the dyno graph is pretty level from 4000 rpm to 5500 rpm at 650 ft-lb. Now, that's at the knock limit with 93 octane pump gas and 9.4:1 static compression ratio so there's pretty much nothing to be found at that rpm band.

After 5500 rpm, however, the stock cams fall off the face of the earth. To compensate for this, we would ideally like increase the boost to offset the drop in the natural volumetric efficiency of the stock engine. The goal is to keep the torque at 650 level and the engine right at the knock limit all the way to 6700 rpm. When we tried to do that, the wastegate got pushed open by exaust back pressure and we didn't meet the boost target. The exhaust manifold pressure was 32 psig static, and the quarter coin sized wastegate flapper's spring would simply give and open the gate. Consequently, we couldn't increase the boost pressure to fully compensate for the drop in the N/A torque curve.

As of yesterday, the car has new wastegate springs that hold double the load compared to the old springs. The motor ought to build more boost past 5500 rpm now. The question mark is whether we can keep the boost at or below 14 psig at the mid range with the new spring, however.
Paradigms often shift without the clutch -- https://www.youtube.com/watch?v=cxn-LxwsrnU
https://www.instagram.com/ptuomov/
Put Search Keywords Here
Bazman
Pro
Pro
Posts: 332
Joined: Sun Aug 21, 2011 9:07 pm
Location:

Re: Dyno result for the risky business Porsche

Post by Bazman »

What a cool project. No doubt about it, when Porsche build a V8 they build a good one. That's a nice power curve for any 5 liter motor on pump gas. Not many V8's that size can make 300ft/lb from 2000rpm and still maintain over 600 between 3500 - 6000. Very sweet ride
User avatar
ptuomov
HotPass
HotPass
Posts: 3036
Joined: Fri Aug 07, 2009 3:52 am
Location:

Re: Dyno result for the risky business Porsche

Post by ptuomov »

Bazman wrote:What a cool project. No doubt about it, when Porsche build a V8 they build a good one. That's a nice power curve for any 5 liter motor on pump gas. Not many V8's that size can make 300ft/lb from 2000rpm and still maintain over 600 between 3500 - 6000. Very sweet ride
Here's a dyno graph of the engine without the turbos installed:
88_dyno_0313_SAE_AFR.jpg
Reflecting back, I think the turbos are adding to the fun. In fact, I am having as much fun as Santa Clause (who, after all, knows where all the bad girls live...).
You do not have the required permissions to view the files attached to this post.
Paradigms often shift without the clutch -- https://www.youtube.com/watch?v=cxn-LxwsrnU
https://www.instagram.com/ptuomov/
Put Search Keywords Here
David Redszus
Guru
Guru
Posts: 8051
Joined: Tue Nov 27, 2007 9:27 am
Location: Chicago
Contact:

Re: Dyno result for the risky business Porsche

Post by David Redszus »

Many years ago, I had the opportunity to ride around the Porsche test track at Weissach in a 928 driven by Helmut Flegl the design engineer of the car. He wrung more performance out of that stock car than I believed was humanly possible. Now I know better. There is always more to be had.
Notice how the dyno graph is pretty level from 4000 rpm to 5500 rpm at 650 ft-lb. Now, that's at the knock limit with 93 octane pump gas and 9.4:1 static compression ratio so there's pretty much nothing to be found at that rpm band.
Notice the double humped torque curve in both the stock plot and the turbo version. A neat trick by Porsche to widen the torque band and make the engine much more drivable for the street.

The static compression ratio of 9.4 might be a bit too high for best performance. We have found that by lowering the CR it is possible to raise boost and produce a smoother, more consistent burn and make more power.
The exhaust manifold pressure was 32 psig static, and the quarter coin sized wastegate flapper's spring would simply give and open the gate. Consequently, we couldn't increase the boost pressure to fully compensate for the drop in the N/A torque curve.
The exhaust gas pressure is not static but varies considerably within each cylcle. Does the 32 psig reflect peak, average, or lowest exhaust gas pressure values?
As of yesterday, the car has new wastegate springs that hold double the load compared to the old springs. The motor ought to build more boost past 5500 rpm now.
We have experienced strange induction oscillations while under full boost at .6Hz, which caused considerable instability. The problem was evenutally traced to a low rate wastegate spring that interacted with the boost controller to produce wastegate instability. A higher rate spring immediately solved the problem.

If I did not have far too many other car projects, I would also develop a 928; it's a neat car.
Post Reply