DynoJet results: Accufab 'X' pipe & SCT Tuner

Since this is my first post to this forum, I thought I would make it an informational one. I purchased my GT about a month ago and have been chomping at the bit to get it on my DynoJet. This is the first Ford I have ever owned. After 280 miles I decided it was time.

I purchased the Accufab X-Pipe exhaust, an SCT Flash Tuner with Accufabs calibration, and an Air Inlet Support.

Since I have a DynoJet in my shop at home, I am able to do extensive testing without regard for time. I made a total of 16 runs this weekend with very good results. What I wanted to do was determine the power increase from the SCT Tuner with the stock exhaust, the Accufab X-Pipe with the stock tune, and the Accufab X-Pipe with the SCT/Accufab tune.

The following graphs will illustrate the results.

On this first graph, RUNFIL~2.DRF is totally stock with the stock exhaust. RUNFIL~6.DRF is with the stock exhaust and SCT/Accufab tune.


On this second graph, RUNFIL~2.DRF is totally stock with the stock exhaust. RUNFIL~7.DRF is with the Accufab X-Pipe and the stock tune.


On this third graph, RUNFIL~7.DRF is with the Accufab X-Pipe and the stock tune. RUNFIL~15.DRF is with the Accufab X-Pipe and the SCT/Accufab tune.


I make it a point to try to duplicate conditions for every run. It took me a few runs to determine what temperature this car liked to run at. It appears the best runs happen between 170* and 180*. All the runs are SAE corrected. The UNCORRECTED numbers for the best run are 563 rwhp and 529 rwtq. The STD corrected numbers for the best run are 566 rwhp and 532 rwtq.

I have made appx. 500 runs on my DynoJet and these are the first runs I have seen that are this jagged. I have seen a magazine article with graphs posted that were also jagged like this. I believe that SCT has another system that will allow me to log and modify the ECM. This is what I will purchase next. I typically use a Racepak data acquisition system to log my runs but I was unable to hook it up for a number of reasons.

I also weighed the factory muffler and the Accufab 'X' pipe. The factory muffler weighs 55#12oz while the Accufab 'X' pipe and brackets weigh 13#. This amounts to a weight savings of 42#12oz.

All in all I am very impressed with the Ford GT. Did I mention this was the first Ford I have ever owned?

Steve

Matt, over 520 sounds real good for torque. I am a little surprised about the horsepower. Was your's dyno'd on a DynoJet? Do you recall the engine temp and the air conditions?

I had a brief conversation with John @ Accufab when I originally placed the order. I asked for his opinion on the big difference in power between GT's and he said it was due to how the cams went into the motor. Since the assemblers are not allowed to dial in the cams they have to rely on the manufacturing tolerances of the keyways, etc. Evidently there is a wide variance that is allowable and this makes up the difference.

Since a cam change requires pulling the motor, I will live with it for now.

Steve

everetto said:

Good info Steve, and nice segmentation on your dyno tests. In both cases your "stock" curves drop off between 6000 and 6500 rpm - and it looks like the A/F curve also dropped off (rich) because it appears to go off the plot with the y-axis scaling that is in place. Are your stock curves without the air inlet stiffener, and if so, do you attribute the A/F richening between 6000 and 6500 to the air inlet collapsing (as has often been reported)? Or, if the air inlet reinforcement was in place for the stock curves, maybe the stock tune is responsible for the A/F richening, and the dropoff of the torque/HP curves between 6000 and 6500? Thanks again for the plots.

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Thanks! I put the air inlet stiffener in before running any tests. The stock tune is 100% responsible for the A/F richening above 5900 rpm. The lowest number that can be recorded is 10:1 so I really don't know just how rich it was. As far as I am concerned, even the SCT/Accufab tune is too rich above 5100 rpm and way too rich above 5600 rpm.

I don't have any experience with superchargers but I do have a fair amount of experience with turbochargers and nitrous. With the turbochargers, I am able to run between 12.25:1 and 12.75:1 safely and get real good results as compared to running under 12.0:1.

I am looking forward to more experimentation.

Steve

jaybnve said:

Steve, great post! Very interesting data. Nothing like having your own dyno to get actual data, rather than opinions. I myself have a Superflow 901 dyno cell in my shop. Too bad its such a pain to get the GT engine out, or I'd put it on there...

I have to say I think you may be pushing the envelope a bit with the 12.5:1 A/F on your turbo motors. I've always believed running 11.5:1 or 12:1 is much safer, especially if you are relying on pump gas, which may vary somewhat in quality. I have a 490" supercharged FE Ford engine in my 69 Mustang, that makes 1200 HP at 11.7:1 A/F. It goes up to about 1265 at 12.5:1, but the exhaust temps jump by nearly 200 degrees when I run the A/F there. So, I'm pretty cautious about going over 12...

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I am wondering what your exhaust temps on the 490 are? I do not have EGT's on my turbo deal but I do on my 542" and 632" BBC motors.

My turbocharging experience is with a 1990 Callaway Twin Turbo with a 350 TPI motor. My maximum rwhp through the mufflers is 650 - not exactly in the same ballpark as your 1200-1265! Since I am unable to get any EGT readings on the turbo motor I watch the spark plugs really close. So far everything is perfect in that A/F range. I have made over 100 dyno runs on the Callaway with the zero motor breakage. I have wounded the turbos, however.

I am jealous that you have an engine dyno. I keep threatening to put in a DTS dyno but it is an incredible amount of work not to mention the disruptions. I am not properly motivated at this time to do it.

Steve

427Aggie said:

It was a dyno jet...I did it Saturday and the temps were probably in the 80's I really didn't bring the engine up to full running temp so it probably was lower than I would want.

I am curious on the key for the cam? Wouldn't you be able to degree the cam without replacing the cam?

Matt

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You can definitely degree the cam without replacing it. My "a cam change" reference should have been "degreeing a cam". Thanks for the correction. I guess it's obvious what I have on my mind. :biggrin

Not ever having worked on one of these motors I purchased a service manual and it states in there that the motor has to be pulled from the car to remove the engine front cover. This is a necessary step in order to gain access to the gears/chains.

As far as the engine temp goes, it seems that the higher the temp the more power it made. Of course, 180* was as high as I dared to go. Does anyone else have any experience with temp/power for these motors?

Steve

tmcphail said:

Move smoothing to 5 in Winpep and see how the graphs change

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Smoothing definitely gets rid of the jaggedness on the graph. Unfortunately it just masks the issue and the issue still remains. Unless this is not an issue and all of these motors display the same tendency. Are there any more DynoJet graphs of these supercharged motors around?

Steve

jaybnve said:

Peak exhaust temperatures range from 1120 to 1250, depending on the cylinder, when running at about 11.7:1, and most go well over 1400 with the A/F at 12.5:1. I have Inconel exhaust valves in the motor, and they are supposed to be good for 1600 degrees, so 1400 is OK, but nevertheless I prefer to keep them a little cooler if possible. Not that you can't run up at those A/Fs, and you obviously have had good results that way. It's just a matter of how much safety factor you want, that's all. At this point with the car, I have not yet been able to get the power to the ground effectively, so running closer to the edge doesn't make much sense in my case. At least not yet.

The dyno is great, and you are correct that it is a painful process to set it up. It took me about three months and $8K in overhead costs before I even rolled the stand into the dyno room. To be honest, I'm a little jealous of your Dyno-Jet :lol . I really need one of those things. And a flow bench. It never ends...

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My nitrous stuff ran 1400* - 1450* with no problems. The car made 1192 rwhp with stainless steel exhaust valves. After pulling the motor apart because of a rod bolt issue, the exhaust valves looked exceptional and I was able to reuse them.

I'm with you on the flow bench as well.

Steve

tmcphail said:

And the issue your referring to is what ? My goal was not to mask anything. I cannot speak for this vehicle on this dyno. It appeared to me that he was new to using a dyno and noticed smoothing at 0. Almost everything will exhibit some sort of jaggedness without smoothing

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The issue I am referring to is the jaggedness and what it represents. I have made over 500 runs on my DynoJet and have NEVER seen this kind of jaggedness. This includes some extremely high horsepower naturally aspirated as well as nitrous fed cars. If this is normal for these motors than so be it. I am just looking for some feedback.

Steve