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New Supercharged 1990 GT Results

 
Old 10-18-2004, 02:38 PM
  #46  
Tim Murphy
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Originally Posted by Gretch
Tim, It is an "upgrade", right??????

Yep, If it works as planned I will send one to everyone.
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Old 10-18-2004, 03:19 PM
  #47  
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Originally Posted by BrianG
Tim, that looks like a GREAT idea. A dynamic tensioner with controlable preload !!!

Simple, yet elegant!
Originally Posted by Tim Murphy
If it works as planned I will send one to everyone.
<--- That's Tim making sure the preload is juuuuuuust right.

You GO boy!
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Old 10-18-2004, 03:38 PM
  #48  
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BrianG said: "A dynamic tensioner with controlable preload !!!"

Now add hydraulic dampening and then we'll have a proper timing belt tensioner!
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Old 10-18-2004, 04:24 PM
  #49  
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Originally Posted by PorKen
BrianG said: "A dynamic tensioner with controlable preload !!!"

Now add hydraulic dampening and then we'll have a proper timing belt tensioner!
"damper" as in: to damp. "dampener" as in: to 'pee upon'

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Old 10-18-2004, 06:04 PM
  #50  
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Video available -

This Schwarz/Schwarz 1990 GT install (that this thread is about) can be seen running on the dyno here:
http://www.928motorsports.com/ourvideos.html

Right-click on "32v Install" and save to your PC before running it for best results.
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Old 10-18-2004, 06:15 PM
  #51  
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Originally Posted by Quick Carl
Here is the deal on the squiggley lines...
...12:1 air fuel ratio and the squiggly lines almost completely disappeared ...
This would support Donald's 'pressure wave resonance' theory.
We actually poicked up a little more HP at 12:1 air/fuel ratio too.
That makes perfect sense as the theoretical maximum power a/f is 12.6.

... dyno operator ... suggested ... 3rd gear pull... lines were very much smoother in 3rd gear. He said ... rate of sampling of the DynoJet ... 3rd gear pull ... 4 seconds long where in 4th gear the pull lasted maybe 7 or 8 seconds so there were many more samples taken. Not sure if that is true - but the 3rd gear pull was almost perfectly smooth compared to the same pull in 4th gear.
Pardon the hack job on the quote.

The above is why, in my first post, I mentioned the measurement technique. Out of context of the DynoJet if you are tracking a pure sine wave signal and sample every 360 degrees (or 2*PI radians) you will 'measure' a straight line. That's very smooth compared to sampling a sine wave every 180 degrees which gives your a sawtooth.

It all comes down to how many samples the Dyno can record during a pull. The more the better - up to a point. The DynoJet needs only to measure velocity of the drum, engine RPM and time. I can only think of a few sources of inaccuracy - RPM measurement and tire slippage. The former may tie in with 'grounding the chassis' during a pull.

Honestly - they went away in 3rd gear,
Understanding the number of samples taken in each pull is the key to determining if the squiggly lines are real or not along with any understanding of the accuracy of the RPM measurement. How accurate is inductively-measured RPM?

Answers from the DynoJet website:

RPM accuracy: +/- 1/10th RPM, timing 1 microsecond, drum speed 1/100th MPH.

That's pretty darn accurate and leaves only tire slippage as a source of measurement inaccuracy. (Unless, static or other electrical effects threw off the RPM measurement.) It also means that the Dynojet can take as many samples as it pleases. From eyeballing the original graph it looks like samples every 50 rpm. That's about 14 samples per second given a 7 second run from 2000 rpm to 7000 rpm. Child's play in terms of rate for the DynoJet.

It would be interesting to get the raw data (e.g. each individual measurement) from the pulls. How many samples? They should be stored on the DynoJet's computer and available in a tab-delimited or CSV format or - worse case - a printout.

I'm not convinced of anything yet - other than Tim's kit bolting on a seriously cost-effective amount of power - but I think those squiggly lines at 11:5 in 4th gear may be real.
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Old 10-19-2004, 12:58 PM
  #52  
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I believe the inertia of the drums would preempt such sudden variances in the curve...

If they were "real", you would have experienced a horrible fluttering vibration on the dyno.

C'mon guys.
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Old 10-19-2004, 03:42 PM
  #53  
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First, let me re-state that I have no conclusion. I'm trying to elicit more information and more understanding. The squigglies could be real or a problem with measurement - or maybe a little of both.

Originally Posted by Old & New
I believe the inertia of the drums would preempt such sudden variances in the curve...
The inertia of the drum is resistance to acceleration. The variances in the curve simply show that the acceleration of the drum varied - cyclicly with small periods of very high acceleration followed by merely high acceleration. Or IOW - all positive acceleration just sometimes more-wildly positive than otherwise.

If they were "real", you would have experienced a horrible fluttering vibration on the dyno
The biggest up/down variation is - by eyeball - about 20 ft-lbs from 4.5k to 4.9k with three cycles. At that point with over 350 ft-lbs on tap, 20 ft-lbs is less than 6% variation. I do not think buttometers would notice a 6% variation that cycles three times in under one second and then is more-or-less steady.

What is the threshold sensitivity of the average buttometer?

If they were "real",...
If they are not real then from where do they come? All guesses and/or informed opinions accepted...

They are not the result of too-few samples. Quite the opposite. The 5+% squiggliness we see is far more than what one would expect given the stated-by-the-maker accuracy of the DynoJet. If they are in fact by-products of measurement - either induced by measurement or uncharacterized noise - then there is a way to characterize and quantify the effect. A 5+% measurement variation is pitiful at this macro scale.
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Old 10-19-2004, 03:51 PM
  #54  
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Originally Posted by Quick Carl
... we romped on it for 200+ miles and never hit the knock sensors once. Not once. Hit the RPM limiter once -but never the knock sensor.
Carl, just confirm: did you use The Hammer after the run to read-out accumulated knock codes? Or did you have it hooked up during the romp?
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Old 10-19-2004, 06:33 PM
  #55  
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I'm going to email the dyno owner and see if he cannot email me the raw dyno data files for you...
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Old 10-19-2004, 06:45 PM
  #56  
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Originally Posted by Quick Carl
I'm going to email the dyno owner and see if he cannot email me the raw dyno data files for you...
That would be cool. I would put those together with three other sets of GT raw data for comparison and manipulation purposes.
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Old 10-19-2004, 07:54 PM
  #57  
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Originally Posted by Quick Carl
Lag is right on the money - I just finished looking at the video from the Dyno Shop last night, and at the very end of the pull you can hear the belt squeel.
I never heard that from inside the car.

I had a thrown my video camera at a kid that was gawking at the beautiful 928 and asked him to video a couple of the pulls. I can hear the belt squeel on only one of the 2 piulls he taped.

I agree with Lag - it's hard to know how much to tighten a new SC belt - you want to go a little easy on the bearings in a new supercharger until they bed in a bit. Also - the rate of acceleration on a dyno that produces belt slippage will never be duplicated in the real world.

From Andy:

1) the Murf kit does not require a hole in the WWasher reservoir.
2) the kit does not require R&R of the intake manifold.
3) the kit does not require replacement of the knock sensors.
4) the kit does require removal of the stock 24lb injectors and replacement with 30 lb injectors that are provided.

"Non-Invasive" in medicine means not entering the body. In engine mods, it means not enteriing the engine. The Murf kit and the 928M kit are non-invasive, true bolt-on kits.

Remember that there is not "one right way" - there are a variety of ways to get more HP out of any motor: Boring, stroking, nitrous, turbo, roots supercharger, twin-screw SC, centrifugal SC, axial SC, fuel additives; and they ALL WORK if designed and engineered correctly. Each method has its pluses and minuses and unique characteristics.

It is not neccesary to put down another's product because it is different than your own. Point out the differences and leave it at that.
Yep Carl, I just watched the video of the GT on the dyno and the belt squeal is definitely there on the first run. No question about it, there is 30+ RWHP to be had with a non-slipping belt. I just did a quick spin in my car and made 14lbs boost using the die spring on the tensioner. If it holds 14 psi it will certainly hold 8 psi. Once I receive the springs I will send one to each of the Murf928 SuperShark owners.


Just to add to what Carl has stated above:

It is our policy to be as forth coming with information as we possibly can with all of our customers. Those that have dealt with me personally know that to be the case (at least I hope you all do . When asked how we accomplish certain tasks we will tell you EXACTLY how we do it because we want to answer any and all questions you might have, no surprises when UPS drops it off. The cost of our kitsĺ include 100% brand new components with all the factory warranties intact. Although we don't recommend it, if you wanted to source some used parts on your own, such as the supercharger, SFMU, gauges, injectors, blow of valve..etc, we will be happy to deduct the common retail cost from the Murf928 kits. With that all being said, I have to amend an earlier statement that I made regarding permanent modifications.... I forgot that you have to break the bracket off the passenger fuel rail that holds the plug for one of the knock sensors or it interferes with the intercooler. This will not be required on the stage one kits. Sorry for the oversight.

Last edited by Tim Murphy; 01-06-2013 at 10:04 PM.
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Old 10-19-2004, 08:13 PM
  #58  
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Worf,

I think the question of fluctuation is one for the dyno manufacturer. I'll buzz them tomorrow.
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Old 10-19-2004, 09:38 PM
  #59  
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Originally Posted by Tim Murphy
... have to break the bracket off the passenger fuel rail that holds the plug for one of the knock sensors ...
Tim, my '94's right side fuel rail does not have that bracket. I suspect that it may have been deleted in later years (after '91 perhaps) and that a rail without the bracket could be ordered thus removing one non-reversible modification. The PET shows the same part numbers for '88 - '95. Nevertheless...
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Old 10-19-2004, 09:46 PM
  #60  
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Originally Posted by Old & New
I think the question of fluctuation is one for the dyno manufacturer. I'll buzz them tomorrow.
I completely agree.
I'll buzz them tomorrow.
Cool. I hope they are forthcoming. It is my suspicion that the DJ might produce the squigglies if there's harmonic vibration on the drum (due to for instance a hopping wheel) and/or if the inductive pick-up misses a pulse from a plug wire every once in a while (<1% might be enough.)

Regardless, they should have some idea...
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