UK952

It would be worth getting a wideband (air fuel metering) system installed to allow you to keep an eye on the fuelling at all times to potentially save the engine from damage. In the past I had a vacuum / boost pipe come off the fuel pressure regulator which made my car run scary lean on boost.
Tony

RolexNJ

Jason Judd: Screw any dyno for now, you have a major A/F issues! Get that addressed first and foremost, before worrying about which dyno is accurate or performance. Right now, you have no idea how your car is running, especially since you don't have a wideband or a read-out from the dyno shop too? No offense at all my friend.

As a few people said on here, and I will say it too, it just takes a few seconds of the car going that lean (like yours did) and the engine can let go! It almost happend to me one time, and I just about had a heart attack. It all got down to having a horrible A/F, and running very, very lean in various spots for me. If I were you, I would hold off on the dyno, even driving the car until you either install a wideband and/or talk to the builder of your car. Don't even take it around the block and hit a little boost. I'm not kidding, you could easily blow it.

Not that this is important for you now, but I can say from several experiences, that Dynapacks are harsh on the 944Ts. I can't speak about any other cars for sure. If you do a search, you will find threads where people talk about how hard these machines are on our cars. I had one experience back in 2005. In short, I had a Spec Stage 3 Clutch, which is rated for over 500 BHP +. I did a few dyno runs @ 15 PSI, and "several" times had the dyno shop call me saying that my clutch is burning and slipping. I said to myself, no way the clutch is brand spanking new. I can't give you a technical reason as to why, but it happend to me with the same shop with like 4 runs. I told them to stop. I've been to a Dynojet, multiple times with Lindsey Racing where we put down 460 RWHP @ 18PSI on pump gas, and not one time did my clutch smoke or slip. Then, I did multiple runs on a Mustang dyno too at various PSI levels, and the clutch never slipped or smoked. And I went to the same dyno shop that Special Tool goes too all the time, actually it is his second home. Personally, I would never, ever use a Dynapack ever again for that reason alone. Trust me, there are people on here who will attest to this too. But as I said, forget this pal, you have A/F adjustment and monitoring issues that need to be addressed first.

Geoffrey

PorscheDoc, I think you'll want to check your facts because your post is incorrect. The Dynapack Dyno has all of the simulated mode functions a Mustang has with the exception of the 1/4 mile shootout mode which is not useful for engine mapping. Further, it has the capability to steady state tune an engine, a function which the Mustang dyno does not do very well, and certainly not well enough to measure torque changes in 1ft/lb range like a Dynapack or Dyno Dynamics dyno which allows for proper setting of ignition timing. It also has the ability to hold an engine at 900rpm in any gear where a Mustang dyno has so much inertia because of the attached flywheel that you must start the car on the rollers in first gear and shift through until you get to a higher gear leaving the lower RPM ranges unavilable for tuning. The Dynapack and Dyno Dynamics dynos both can start off in any gear. The Mustang dyno is certainly worlds better than a Dynojet

The clutch slipping issue is not really a dyno issue, but rather an issue with the car. Any dyno that can hold a load steady state (Dynapack, Dyno Dynamics) with a high degree of accuracy and speed, more like an engine dyno rather than a chassis dyno will identify weaknesses in the drivetrain. The size of the 944 clutch assembly is small compared to the torque capability the engine produces. I have also had 944T cars on Dynapack and Dyno Dynamics dynos have their clutch slip as the engine rolls through peak torque, particularly in the higher gears such as 4th or 5th. I have also had 944T cars with clutches that do not slip, and I've had other cars where the clutch slips. A Dynojet dyno has a huge interia mass which is why it only takes a few seconds to complete a run and does not realistically load an engine. It certainly is less harsh on an engine, but is not as accurate.

Rick DeMan

"The saying we typically go by, is "If you want to tune a car properly, buy a mustang dyno....if you want to make money....buy a dynojet." Being that the mustang dyno has a lot of capabilities to tune under a simulated load, etc that a dynojet or dynapak does not have."


This statement makes me believe you've never seen or used a Dyna Pack dyno. The Dyna Pack dyno is the closest thing to an engine dyno you can get in a chassis dyno. You can load and hold any RPM range at almost any throttle position. It uses a MOTEC PLM wideband meter built right in. It's probably the best chassis tuning tool you can own...

The car in question here was tuned on this dyno 2 years ago, checked over and over again thru the years. It was always tuned to 12-12.5 afr's. I believe it's survived MANY track hours at WOT with the existing tuning. I have a very hard time believing the AFR's reported. If they were correct it would have burned up a piston a LONG time ago...

I would almost have to agree with you Raj....something fishy going on here..

Porschefile

I'll second the positive comments about Dynapack dynos. I think I am going to tune both of my cars on one. My boss has gone through several 240sx's, a 350z TT, and built R33 Skyline all tuned on the same dynapack. He has dyno'd on a few various mustang and dynojet dynos. Mustangs do tend to read lower than the others, dynojets seem to be a little inconsistant between different dynos, though the dynapack seems very nice (for all of the reasons Rick posted). The steady state tuning possible with Dynapack's is a very cool feature to work with, and the fact that it allows you to tune so low in the rpm really helps allow you to improve overall drivability.

Rick, I've watched the vids of that "gt2" (not sure if it's a real on or replica) on your site. It is nothing short of spectacular! Great work! (was that car the Gt1 class 911 listed in your sig?)

RolexNJ

If I may ask, are you the guys who built and tuned the car 2 yrs ago? What kind of EMS does it have in it? And I would be interested in seeing the dyno charts with the A/F ratios too for when you guys did tune it back then. Do you think you can provide that for us just so we can see it, if you don't mind?



EDIT: I checked out your web site, it is very nice. And great videos too!

Jason Judd

Rick Deman did my job, and we've had no problems with the car. The only problems we've encountered seem to be those that come from the loose nut behind the wheel time to time...Thank God those have been relatively minor compared to when I had a 951!

On a more serious note, why I asked the group about the Mustang dyno was the concern when the other guys showed me their Mustang numbers for A/F. I understand how HP and TQ numbers can change from machine to machine...and those seemed to be within the range.

It was the A/F numbers that had me concerned.

Jason

RolexNJ

Oh ok. Were they the last to tune it? If not, get the dyno sheet print outs from the shop that did the last tune and with the A/F ratios too. That would help with understanding your A/F concerns.

UK952

and check the fuel pressure regulator vacuum/boost hose is connected
Tony

special tool

This MUST be cheked every time you check the oil.

jgporsche

Just for some Dynapack vs. Other Dynos, Today I dyno'd my 944S on a Dyno Dynamics Dyno - results were that the Dynapack was 10whp and 10WTQ lower than the Dyno Dynamics. I dyno'd my 951 on the Dyno Dynamics and number-wise it was where it was supposed to be.

Rick DeMan

If anyone would like to see the Turbo conversion, just follow the link.

http://www.demanmotorsport.com/deman...lery.php?pid=2


Any turbo car running 14.0 AFR's you should be concerned about. If the #'s were accurate on the dyno run then I would get it checked out...FAST. If the hose to the Fuel Pressure Regulator was removed to record boost on the dyno that could be a source of the problem.

Did your new mechanics investigate? What was done about it?

Also there is no need to replace your existing ECU...there's no performance gain in doing so. Only recordable functions can be gained with another type...

richard glickel.

Jason,

You've got mail.

Jason Judd

Jeremy Himsel mentioned:
"That's scary high and I'd be very concerned. I guess from 2000 miles away I would question the accuracy of the A/F readings because at high 13's and 14's under boost I'm shocked that you 1. don't hear detonation, and 2. you haven't popped a head gasket. Without knowing information about your boost levels, induction and fuel system it's pretty hard for us to guestimate HP."

Toddk911 suggested:
"Yea, maybe try a different shop and compare."

And, Geoffrey said:
"Anything worth doing is worth doing correctly, it would have prevented you from having a heartattack due to AFR numbers that would appear dangerous."
___________________________________________

So, I took their advice...which was echo'd by many other people...and had an independent 3rd shop do another dyno run; and spent all the time it took, to do it right.

Unfortunately, those numbers were also very high...running over 13.0 for most of the range...while the boost gently climbed to about 17 lbs and stayed there for most of the run.

So, I guess the A/F numbers are correct.. and I need to have this corrected pronto! Good thing it's the end of the season out here on the East Coast.

By the way, the 3rd dyno was done on a dyno dynamics brand dyno...Their numbers were nearly identical to the Mustang numbers.

Thanks for all the input everybody!

Jason

toddk911

"By the way, the 3rd dyno was done on a dyno dynamics brand dyno...Their numbers
were nearly identical to the Mustang numbers."

Well at least that is settled

I am still unsure how you did this big of a project with no wideband, but in anycase you now have accurate a/f (wideband) data and only need to richen it up with what ever you are using as your fuel control.