Low HP on Dyno

Hey Guys -

I had my car dynoed today to get a baseline hp/tq number before I started adding headers, intake, etc. I used Pro Dyno in Fort Mill, SC that has extensive experience with all sorts of Mustangs. They have a DynoJet and I was about the 7th or 8th GT350 Dan had dynoed. My car only made about 430hp and Dan immediately said that he thinks I have bad gas but I've always put 93 octane BP fuel in it. Anyway, I was disappointed and now concerned that maybe I have a factory freak with low horsepower. I don't really believe this though because I noticed the car seemed more sluggish lately. So maybe I just got a tank of lower octane gas somehow. Dan said he could see where the car tried to make more power on the top end and the computer looked to be retarding the timing.

So I'll run this tank out and refill and maybe even add some Torco octane booster and dyno it again to see what's going on.

Any other ideas?

Datalog?

Yeah ... might pick up a NGauge to do just that. I can't keep going to dyno every week after I fill up with gas.

[MENTION=7311]Grimace427[/MENTION]

There was a head to head GT350 dyno here in Atlanta recently at a dyno day and one got 30 more HP than the other... they both had zero modifications.

Compression test and a leak down test will let you know if you have an issue internally. That would be my first step

wildcatgoal said:

There was a head to head GT350 dyno here in Atlanta recently at a dyno day and one got 30 more HP than the other... they both had zero modifications.

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Would be interesting to know which Dynojet model they are using; whether they're consistent with strapping force, wheels/tires, etc. I've probably dyno'd about 75 BMW M3's, and there were a few surprises. For example, there was a cutoff in 2011 where bone stock factory ECU software gave about 20 whp more than pre-2011 ECU software. This lead to a craze where everybody rushed to get their ECU software updated. Lighter wheels show more whp on a dynojet when run on the same car and same weather conditions (same DA). Stickier tires seems to give less whp presumably due to the extra friction. And of course there's weather conditions that play a factor too. Just saying there's a few variables to consider that might explain the differences.

Post the dyno chart, it might have some clues. You can also post the dyno DRF files for people to take a look and analyze.

To many variables to say why the difference specifically. You would literally have to run the two cars right after one another in the exact same conditions to have consistent results. @nastang87xx is correct about dataloging to check for abnormalities. Chances are its just a "glitch in the matrix"

my car has always run best when hot. Might be an interesting test to keep doing dyno pulls from barely warm till its quite hot and see how the chart changes.

[MENTION=28945]PencilGeek[/MENTION] I remember you from my days on the BMW forums. Good to see you here. I will post the dyno chart later for review.

I am going to dyno the car Friday with Torco added. I'll let you know how my numbers compare. We have 93 here and I added 32oz of Torco last week and the tank is about gone. I am going to add another 32oz bottle and fill up tomorrow and according to the math it should have me around 98 or 99. Not sure on what dyno they have but I will find all of that out.

Houston Kid said:

I am going to dyno the car Friday with Torco added. I'll let you know how my numbers compare. We have 93 here and I added 32oz of Torco last week and the tank is about gone. I am going to add another 32oz bottle and fill up tomorrow and according to the math it should have me around 98 or 99. Not sure on what dyno they have but I will find all of that out.

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I'm not familiar with the Shelby ECU, but in some "target based" ECU's, over octane can hurt performance. In a closed-loop ECU ("target based ecu"), the ECU tables specify timing targets and AFR targets, and the ECU reads the engine and lambda sensors and does the math necessary to adjust spark, fuel, cams to make sure the engine hits those targets. When the engine can't hit the targets, you get less performance. Once it hits those targets, there's also a point of diminishing returns. Over octane can hurt performance on these types of ECU's just as under octane can.

Again, I have no idea what type of ECU the Shelby has, so I'm in a learning curve about it. The tuners who have worked with this platform could probably comment about the ECU and whether or not there's a point of diminishing returns on adding octane.

PencilGeek said:

I'm not familiar with the Shelby ECU, but in some "target based" ECU's, over octane can hurt performance. In a closed-loop ECU ("target based ecu"), the ECU tables specify timing targets and AFR targets, and the ECU reads the engine and lambda sensors and does the math necessary to adjust spark, fuel, cams to make sure the engine hits those targets. When the engine can't hit the targets, you get less performance. Once it hits those targets, there's also a point of diminishing returns. Over octane can hurt performance on these types of ECU's just as under octane can.

Again, I have no idea what type of ECU the Shelby has, so I'm in a learning curve about it. The tuners who have worked with this platform could probably comment about the ECU and whether or not there's a point of diminishing returns on adding octane.

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It's just something I want to know after reading the 91 vs 98 thread. I am going to go back next week and dyno again with just 93 to see for sure if any gains can be had by running higher than 93. I will pick a day that the humidity and temp are similar to Friday's and do it then after I run two tanks of 93.

Houston Kid said:

It's just something I want to know after reading the 91 vs 98 thread. I am going to go back next week and dyno again with just 93 to see for sure if any gains can be had by running higher than 93. I will pick a day that the humidity and temp are similar to Friday's and do it then after I run two tanks of 93.

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Thanks, I'll go read that thread.

Here is the dyno chart (one I don't plan to frame) for your viewing pleasure. You can see on the third run (green) where at 7K RPMs it looks like the ECU tried to bump the timing it appears. I think my next step is new tank of gas, Torco, and data logging to see if timing is still being retarded.

I welcome feedback after seeing the chart.