I can offer a few thoughts on this...

1. Use the largest possible fan (four or five feet tall) blowing air at high speed directly toward the front of the car. This will help keep the radiator working well and the engine coolant temperature under control.

2. Use two smaller fans blowing on the side intercoolers if possible.

3. Don't worry about blowing air into the intake at 100 plus mph. Our cars don't really have 'ram air' induction. Even if they did, that effect would be miniscule in comparison to how much air the turbochargers are sucking in once they start to spool up.

4. Don't worry about having too much fuel and not enough air. Our PCMs typically inject fuel based on the amount of air detected flowing by the MAF (mass airflow) sensors, which are mounted in the intake tubes. Some tuners undo this, but this is the best way to tune these cars in my opinion.

 

Thanks for the good info.

The last WOT pulls I had done last month did not have much air being blown on the engine.

As it turns out the tech also ran my 4 dyno pulls in 3rd gear.

This wasn't mentioned when I had it done but only after I asked a week later.

This is also the same gear K&N is running their dynos tests in when they test a new CAI.

I suspect Hennessey and a few other tuners are also running in 3rd gear because they all get the same stock / baseline ATS-V and CTS-V RWHP & TQ.

I sent a message asking Hennessey what gear they run their WOT Dynos in but have received no reply to date.

About a month ago I was told by a Cadillac engineer who worked on the CTS-V2 and V3 programs that a properly run dyno on a stock 8A production ATS-V will produce about 375 RWHP and not the 425 - 450+ RWHP that is so widely reported on the internet.

He didn't mention anything about being tested in 3rd gear though.

That is exactly the RWHP that is being produced by stock ATS-V's at K&N, Hennessey and D3 and several other vids on YouTube.

So it turns out my BRUT4L ATS-V pulled a 3rd gear dyno that resulted in 450.02 RWHP and 445 RWTQ.

At the time she had a WXM tune + WXM exhaust + WXM downpipes.

Now it has the P/N 63-3093 K&N CAI in place of the stock.

It will be interesting to see what the K&N CAI brings to the party when I have it dyno'd again this coming week

IMPORTANT NOTE: I am not advocating anyone's stock RWHP results to be right or wrong.

And I know bringing Hennessey into this discussion adds no value in terms of honesty.

I'm just reporting what happened to me. Unfortunately I don't have a stock 3rd gear pull to compare what others have gotten.

 

IMO, if your simply running a dyno to show before and after gains it doesn't matter to much which gear you use.

If your running a dyno to determine your max HP then the only true gear to use is the 1 to 1 gear. I believe that is 6th in this car.

The only reason I can surmise why some aftermarket bolt on manufacturers would use 3rd gear is the car isn't entering it's max power (untuned). When the car gets to it's max torque numbers the cars torque management will kick in to keep numbers where it feels it should be. That action by the ECU would negate any significant gains made.

This is why without a tune you never really take advantage of the added flow of an intake, DP, or exhaust.

If you're paying for a dyno request it be run in 6th gear so you get real numbers you can compare with.

By the way, K&N's dyno numbers on their website say in small print at the bottom that the dyno shown is on a "similar" car. In other words, it's not necessarily on an ATS-V.

 

Q) If there is little to no air blowing directly into the air intakes or directly on the engine in an attempt to feed those two turbos
will that not effect the outcome of the test?
A) Turbos are not like superchargers where they rely on intakes to make boost. The lack of airflow across the car is concerning in terms of things heating up. Hence the reason why people make dyno pulls in 3rd gear because the run is shorter. Making a run in 6th gear in an automatic will take longer and heat will be a major factor. Will your rwhp and rwtq numbers be skewed if you dyno in a gear higher than 1:1.....yes the rwhp numbers will be lower.

Q) I'm thinking that a modern engine like the LF4 will have MAF meters that will be expecting 100 mph type winds rushing into the air intake because the rear wheels in fact are rotating at such a rate but will actually get diddly squat in terms of air flow and the ECU will then dial back on the fuel and you will end up w/ a HP loss.
A) A Mass Air Meter measures air mass, and from that value it calculates load. Load is the mass of air being ingested by the engine divided by the engine's potential for air mass if all of the cylinders were full at the same time.

 

Q) If there is little to no air blowing directly into the air intakes or directly on the engine in an attempt to feed those two turbos
will that not effect the outcome of the test?
A) Turbos are not like superchargers where they rely on intakes to make boost. The lack of airflow across the car is concerning in terms of things heating up. Hence the reason why people make dyno pulls in 3rd gear because the run is shorter. Making a run in 6th gear in an automatic will take longer and heat will be a major factor. Will your rwhp and rwtq numbers be skewed? Yes, they will be.

Q) I'm thinking that a modern engine like the LF4 will have MAF meters that will be expecting 100 mph type winds rushing into the air intake because the rear wheels in fact are rotating at such a rate but will actually get diddly squat in terms of air flow and the ECU will then dial back on the fuel and you will end up w/ a HP loss.
A) A Mass Air Meter measures air mass, and from that value it calculates load. Load is the mass of air being ingested by the engine divided by the engine's potential for air mass if all of the cylinders were full at the same time.

What he said ^

The engine and turbos don't requires fans or speed to get air, we don't have a ram air. They suck the required air through the intake whether the car is moving or not. Strong fans blowing on the intercoolers and radiator are to keep things cooled down so no heat soak.

What will happen is if there's no airflow the engine heat will eventually saturate the engine bay and also the intake. As a result the intake temps will rise and lower your performance.

 

when I got my last dyno I was told by a reputable tuner that they use 5th gear rather than 6th for safety reasons because of the higher speeds of 6th gear. When I had my car dyno'd on a dynocomp I asked them to use 5th for comparison purposes but the numbers were a little lower than expected. They tried again in 6th gear and that brought the numbers where they should have been. 6th gear is your 1 to 1 so it will be the most accurate measurement when comparing to your stock power +/- drive train loss. Once you add gearing you change the power delivery, that's the purpose of gears.
Lower gears will exhibit more torque and higher gears less but keep in mind, this is all still being controlled by the ECU's power management. In other words when you're in 3rd gear you're going to get the power the ECU allows for that gear. The stock ECU does not allow full rated power in every gear, especially lower gears.

I can see however, when running a comparison, if you run a 3rd gear pull for before and after and show a 100hp gain it stands to reason that would apply to your stock numbers as well. In other words if you're at 464hp at the crank you are probably now at 564hp. Take away the 15% DT loss and you're at 479HP to the wheels. This, to me, defeats the purpose of running the car on the dyno to establish you actual peak numbers but this is the kind of math these aftermarket intake manufacturers use. That's why they always disclaim, "above charts run on a similar car, actual results may vary" or something to that effect.

 

Something is screwy.........when WXM finished their upgrade on my ATS-V back in Nov. 2017 they tested the results using their Mustang Load type Dyno (not an DynoJet inertia type) and recorded 502 RWHP / 469 lb-ft TQ. Then I have it retested on a Dynojet inertia dyno (in 3rd gear no less) and the result is 450 RWHP / 445 TQ.......really? This is a perfect example of why I believe...............I'll stop right there. Common sense says one (possibly both) of these dyno tests are useless crap.

Agreed. I have considerable experience with dyno tuning and can tell you that it's very common for DynoJets to report extremely consistent numbers from run to run, day to day and dyno to dyno. Assuming the same correction factor and smoothing are used I would expect to see numbers within +/- 3% consistently.

 

Again, Load is the mass of air being ingested by the engine divided by the engine's potential for air mass if all of the cylinders were full at the same time. Using a NA engine as an example, and in a perfect world, the load of 1 is max load...............so the vehicle is at full power. As far as transmission gears goes, engine management is not looking at a variable like gears, it monitors RPM. Load and RPM would be variables in the "X and "Y" axis of a table.

 

So by your rationale we should get the same power in every gear as long as the load is the same. Unfortunately that's not how it works.

 

Torque increases until you hit 5252 RPM which is also the maximum VE that that particular engine can obtain. After 5252 the air flow losses due to friction and mechanical losses ( heat ) tend to be the dominant factors after 5252 RPM and become bigger players in your engine and torque starts to drop off rapidly.

Actually, torque does not necessarily peak at 5,252 rpm. That's possible, but rare. What does happen is that horsepower and torque will be equal at 5,252 rpm. This is why their lines will always cross at this point in the dyno chart (assuming they are displayed using a shared axis).

 

You are correct.

The 5252 really is meaningless other than it is the result of Mr. Watts experiment w/ a horse and the resolving the Force, Velocity and Torque equations into the HP = TQ x RPM / 5252 we all know and love.

HP and TQ have different units but for reasons of convenience dyno software have HP and TQ readings taken off the same Y axis.

 

My whole point in this, and again this is based more on other cars that I've worked on, is that the reason I believe some manufacturers use 3rd gear for Dyno pulls is because there's a wider degree of Tolerance with the ECU allowing for changes in power. Once you get to the one-to-one gear you're putting out your maximum power and without a tune the ECU is going to limit that. A particular modification might be good for an extra 20 horsepower but at your max power levels in your 1:1 gear the ECU is going to trim that down.