G Man

You mentioned in your earlier post that your trans is in third by the middle of the block. I had the same issue with my 84' and it turned out that the vacume modulator on the side of the trans was bad and would not hold vacume. Changed it out and got it adjusted and the car shifted much better.

Black928GTS

Not all stroker engine builds have a happy ending. My 928Motorsports stroker buld is a DISATER!

I have been driving 928s for the past 20 years, but have never posted on this site. I originally ordered a stroker engine from Devek, but cancelled that order and when I went back they were out of business. Web searches led me to 928 Developments, and I contacted its owner and was negotiating to have a stroker built when he fell silent. I thought about putting a Chevy engine in it, but turned down that option even though it was turn key and promised with CARB certification. I found the parts previously listed at 928 Devalopments on the web site for 928Motorsports. At the end of 2008, after listening to a sells pitch regarding 928Motorsports engine bulding experience, I ordered a stroker engine from 928Motosports for use with the supercharger I already had on my GTS. I did not get the engine until March of 2010.

I had many many problems with the engine and other parts sold by 928Motorsports, and finally got it running in my car this October 2012, when the water pump quit working and the oil pressure has always been too low - after only 16 miles on the engine. 928Motosports says its one year warrantee has expired and it will not do anything unless I take the engine out and send it to them - and pay them even more than the tens of thousands I have already paid them.

I was very surprised to find that while I was waiting for my engine, 928Motorsports build a similar engine for their speed record run. They sold me a piece of crap engine that did not meet many of the criteria I specified, and delivered it well over a year later. They did nto run or test the engine even though I ordered it with burn in and testing because they needed my intake from my GTS, which I was driving around. It turns out that even if I sent it too them they built the engine on an '85 glock, which does not accept a GTS intake amnifold without cutting on the block. My engine must have been the experimental work done before they built thier engine because it still does not run properly - and may never.

I have it listed on eBay if anyone wants to buy it for parts.

http://www.ebay.com/itm/221159002807...84.m1555.l2649

Just want to warn anyone considering the same mistake I made - it cost me tens of thousands and the use of my 928 GTS for the past two years.

Byron

drnick

Oh dear...

andy-gts

UPdate !!!!I have had the entire exhaust system replaced by greg's awesome stainless headers and exhuast system that is a smaller diameter than the devek level 2 dual 3 inch one that droned badly.....this new system is sweet music,,,,,no drone to my ears.....got it back from the dyno with dual wide band o2 sensors and retuning for new exhaust system and rwhp is down but I am ok, still have the tune and old 3 inch system......

original was 498 and now 462 rwhp.....quite a difference but I guess expected.....does this sound right????

john gill

Different day , different Dyno I wouldnt read a whole lot into it

andy-gts

same dyno , same ambient air temp 68 degree F.....hmmm....this is 24 % loss through drive train...???

or was original results puffed up some how......??????

Strosek Ultra

Andy, is there a thread with pictures of your stroker engine? The smaller exhaust probably made your engine loose a few ponnies. Any engine will loose some power over time depending on carbon deposit build up in the combustion chamber, in the ports and on the valves, especially at the back of the intake valves. The very carefully cut valve seats on ported cylinder heads will get deformed over time reducing flow and the power.
Åke

Imo000

That's a big drop.

Rob Edwards

Both of the dyno results there are SAE-corrected numbers? Got screen grabs of the dyno runs?

Andy, do you have the .bin files of the fuel and timing maps from the previous tune and the current tune? I assume the new tune was pegged to the same AFR map as was in there before? It would be interesting to see how different the fuel and timing maps compare, might help explain the difference, between the obvious change in the exhaust.

SwayBar

I disagree, we're talking 36 rwhp...

Did you dyno it directly before the swap, and then afterwards?

If not, you do not really know when/where the loss occurred.

GregBBRD

Andy:

Was the engine re-tuned to compensate for the additional back pressure or are these results the same "tune" 2+ years apart? (I would anticipate that both the timing and fuel curves would be completely different, for the two exhaust systems.....and I believe that the old power readings we done quite some time ago...not back to back.)

Everyone else:

Before anyone gets all giddy about a loss of power with my exhaust.....there's more to this story, than Andy is relating, right now.

Andy wanted to change the exhaust for one reason...the car was terribly noisy and irritating to drive with the 3" system. (When it was here, I considered the car to be virtually undriveable, because of the noise.)

We anticipated there would be a loss....there's quite a bit more restriction in a quiet 2.5" system compared to a noisy, droning, wife won't ride in it, 3" system. In my head, I anticipated up to a 10% loss. This loss (although not back to back) is 6%....fantastic result, considering the change in sound.

Keep in mind, race cars use open headers for a reason....

For this reason, I also supplied a set of 3" collectors, which Andy was going to attach to the existing 3" exhaust system, for use when he does any "open road" events.

We anticipated that these collectors and existing 3" exhaust, with my headers, would actually work better than the Devek headers, with their various design issues.

I've dyno tested the Devek headers and my headers back to back (open) and know that my headers work better (even before bashing in the one pipe on the Devek system to clear the starter), so the change in headers is only a positive thing.

When the dyno results when my quiet "street" 2.5" system is swapped out for the noisy 3.0" "track" system are done, this will be a far better data pojnt, for direct comparision. (This will also require additional tuning.)

john gill

There are many variables to consider , Pressure , fuel type , temperature , wheel diameter , etc the list goes on .

I assume )that this is a roller type dyno ,

Eg what was the tyre pressure between the 2 runs , barometric pressure etc .

If it is a hub , then the variables are less .(no wheels)
If you change a major engine component eg headers ,CAMSHAFT ETC , YOU CHANGE THE volumetric efficiency of the engine . Some components will better at differnt points then others and will or may require calibration.

Do you have data logs of both sessions on both of the days ?

andy-gts

ah ha....!!!!! this turns out to be apples to oranges......first tune was DYNOJET , this last tune was with a MUSTANG DYNO..... I wasn't there for the dyno which was a retune for the use of the new exhaust system, don't have the bin files but can get them easy enough... I kept the old tune on the lynx system for when the dual 3 inch system goes back on.....but the sound is so nice now ......no drone....

andy-gts

fyi this engine was finished 2011 and has now 6yrs and 25k miles on it.....I am still happy as a clam...!!!

hans14914

Mustang makes a great piece of hardware, and one of the best roller units out there (from a value standpoint for sure) for tuning. They are probably one of the more realistic number generators, and will always be much more conservative than a DynoJet number. This is a hotly contested debate between which is more accurate, and what numbers are the "real" numbers.