Recent threads have highlighted a common problem for those of us with Vararam intakes who wish to dyno tune our engines. Most dynos use a large fan placed in front of the car. This helps keep the engine cool, but does not really simulate the actual air flow that is experienced at higher speeds, either on the road or at the track.

So, the question is: how should we approach optimizing the tuning parameters for a VR-equipped vehicle, especially at the dyno?

PLEASE, let's not turn this thread into another "food fight" about whether the VR works as advertised, or is a myth. Save that for another thread. Those of us who already have the VR are convinced of its effectiveness. What we need to know is how to tune for optimum results.

 

The only way it can be done is to do a road/track tune in conjunction with a dyno tune. The dyno gets you in the ball park, the road/track tune for that final adjustment.

Now of course if someone whants to build a wind tunnel and chassis dyno combo we could have it all.

 

I got a nice PM from Vararam, suggesting that the target A/F ratio should be richened up by a full point or so, which also allows a bit more timing. This will hurt the dyno numbers a bit, but improve street & track performance.

 

I am a road tuner only...backed by going to the 1/4 mile to verify improvements...

 

Or possibly a couple of high powered leaf blowers handheld and directed right in front of the grill opeing during the dyno session.

 

Here ya go.......... http://videos.streetfire.net/Player....AD23CA9564&p=0

 

I would love for someone to stick a pressure sensor inside their vararam and do a 150 mph run. I think many would be stunned by the results or lack thereof.

 

Small air pressure sensors inside the vararam would give absolute air pressure gains at various speeds. (The locations would be critical due to velocity and turbulence.)The engine could be tuned based on this. I've seen this done on roadracing motorcycles. (Kawasaki in particular as they have aerospace expertise also.) They had as much as 1.4 psi increase at very high speed. Good for 17HP.(This was performed back in 1999, so todays technology is obviously superior.) Remember it works like any other forced induction system... the more the throttles are open the more air needs to go there to increase the pressure. The air "force" has to overcome the open throttles. This requires a lot of volume...a lot! Also, remember that "velocity" DROPS pressure. It has to overcome this phenom also.

Sorry to go "all around the board here."

 

Actually, if you run a scan with HP tuners you will notice that the car gets a bit more lean up top (around 100 mph).

 

Just installed a Vararam on a 07 M6 today, car already head a B&B headers/cats/exhaust system. Final Numbers after tuning, 382.8rwhp SAE (Mustang MD-1100SE dyno), and 365rwtq. Anyway you look at it, the intake does work and makes power.

As far as tuning with for the Vararam, if done properly, the PE enrichment should command the desired AFR for WOT based on air flow. A setting of 1.13 (14.7/1.13) commands a setting of 13:1 AFR for example. A fixed value in the PE table will make RPM's irrelevant for tuning purposes. Now the WOT fueling is going to be proportional to the amount of air that is metered. As long as the air metering device is callabrated, then WOT is always going to be the same assuming the LTFT's are negative and go to 0 at WOT.

So if for example, lets say you hit 10000HZ on the MAF in 4th gear at 6400rpm, and the AFR is what you are commanding, then "ram air" affect is good up to 10000hz. Now to compensat for increased airflow higher than 10000hz, you can make repeat the pull in 5th gear, this should increase the MAF hz to 10800 or so at 6400rpm. Now change the MAF table accordingly for the cells between 10000hz and 10800hz. Do it again in six gear, and the MAF hz are going to increase again to, lets say 11600hz, and change the cells between 10800hz and 11600hz. As load increases, the amount of air the engine moves goes up. I wish I had the logs from the car I tuned today on this computer, but what I saw goes something like this:

1st gear@4400rpm-5500hz
2nd gear@4400rpm-6000hz
3rd gear@4400rpm-6500hz
4th gear@4400rpm-7000hz
5th gear @4400rpm-7500hz

This is one of the reasons if tuning is to be done on a dyno, loaded dynos (such as the Mustangs) are so important.

The other way to do this is to use a loaded dyno, and increase the load to the point where you can fulfill a AFR reading for every cell in the MAF Hz vs. Airflow table. Now no mater what gear you're in, or how fast you're going, or what rpm you're at, the MAF is properly metered to the amount of air coming into the car, the VCM is adding fuel as commanded.

The MAF doesn't know how fast you're going, or what RPM you're at, all it knows is how much air is moving past it. Have the correct value for all the cells in the table, and it won't matter if on the street it's measuring more air than on a dyno pull due to the "ram air" effect.

I know it won't be as accurate (as far as power gains) as a dyno in a wind tunnel, but with taking the proper time, you can assure that the AFR at WOT is going to be correct.

 

I don't understand alot of what your saying with all these "ratios" and terms -What I do glean from it is the Varam causes the motor to run lean at speed? or does the MAF sensor and fuel system increase the fuel enrichment when at higher speeds-please explain "In plain speak" My concern is I installed a Varam and purchased a Wet NOS Kit and don't want to increase chances of leaning out my motor. P.S. I also have a "out of the can" Diablo Predator tune #7194 for my 07 if that makes a difference to the above-THANKS

 

Cooling the engine with air flow though the engine bay maybe more important then the so called ram air. Any real CAI works about the same as any othe CAI

 

The engine already comes with a MAP sensor, all you need to do is log that during a WOT run with the stock air cleaner housing, then again with the Vararam air cleaner housing. Any difference in absolute manifold pressure at the same road speeds will be due to the "ram air" effect of the different air cleaner housing.

 

Good thread. I had a helluva time tuning my C5 which had a Vararam on it.

 

look at your MAP sensor. Do a before and after comparison at speed. Most of the gains are from lower IATs.

 

So the lower IAT's are what causes the A/F ratio to run lean at higher speeds?



I was intrigued by Tuner@Straightline's explanation of using the dyno to adjust the cells. Not being a tuner though, I didn't follow all of it.

I have an A6, so I have done my dyno pulls in 3rd gear. That doesn't result in optimal numbers, but for tuning purposes, it's more realistic.

 

You verified this or was this something that was told to you? Datalogging with a wideband(before and after)? How much leaner? At what speeds?

You are getting colder, denser air.... but enrichening your tables 1 full point to compensate for a "ram-air" effect seems a little over optimistic of the expected gains.

I'm not being sarcastic in any way, I know things come off in very different ways when you read them as apposed to hearing them.

 

He was explaining tuning vs load and calibrating the Mass Air to compensate for changes that may occur at speed.

 

 

I don't have a wideband O2 bung on my exhaust, so I have not done any datalogging myself. However, I have been at the track on multiple occasions where I have seen VR equipped cars run lean after their install, confirmed via a wideband datalog and also via AutoTap. Richening up the A/F mix reduced KR, and improved times.

For some of these cars, they had not been dyno tuned beforehand. After the VR install, they had improved times, but no KR. My thought was that the A/F mix leaned out somewhat, but it still stayed under 13:1.

For other cars, they had already been tuned to an aggressive A/F mix. After the VR install, they started getting KR. After richening up the A/F mix, the KR went away, and times improved.

Richening the mix a full point does seem to be excessive to me as well. However, it also depends on the A/F mix starting point, and how much timing is added. When it comes to tuning, I have seen stranger things be effective.

Max, I understand that you're not being sarcastic. I don't really care whether the VR works because of lower IAT's, the "ram air" effect, or the effects of lunar tides. I AM convinced that it does work, and that it results in a need for additional tuning. If richening the A/F and adding timing will do the trick, great. If some other approach is better, I'd like to hear it. I'd also like to understand the reasons why.

Thanks for your input. I've learned not to spit into the wind, tug on Superman's cape, or argue with a world famous tuner. Sometimes all the world famous tuners just don't see eye to eye.