Question about dyno tuning..

[Vette73]

Had a few cars put on the dyno over the past few years....Does it matter if they are running a fan in front of the car ? Is this done to simulate outside air coming into the car, as if it was moving down the road.?

Reason why I ask is because I dynoed both my vettes over the last few years ( ZR1 last week) and both times they did not run the fans....I would guess if you had a ram air effect car it would effect the overall numbers,or, should the fans be running no matter which car was on there?

[efnfast]

I'm pretty sure it's for cooling in the radiator. Poor engine is screaming at 7K with no air flow through the rad. I'd be asking for fans.

[Hog]

The typical fans are there to assist with air flowing over the rad. They provide no "ram air effect" worth mentioning. Most of the fans I have seen on chassis dynos don't come close to approximating the airflow that occurs as a vehicle goes down the road, esp. at any sort of speed. But if the fans are present, I don't see why they shouldn't be used.

Even if the air intake is designed to take advantage of the Ram Air Effect, hp improvements at 100mph are about 1.2%, 2.7%@150mph and 4.8% at 200mph.

A white hot tune on the ragged edge of detonation could be affected by not having air flowing through the rad, esp. on the Corvette where cooling and cooling system packaging don't leave much margin at all.
This where a combination of dyno tuning combined with street tuning are all parts of the ideal all around ECM calibration, just like GM does it in the 1st place.

[Mystic ZR-1]

I'd avoid any dyno operator who didn't run a fan
for the radiator while dynoing a car...

[Vette73]

Yeah I hear from the grapevine it's basically for cooling....As far as the ram air effect I was suprised it has that little improvement in horsepower..

[edram454]

Having had a few cars dynoed, I would only do it if I was tuning the car to run at its max after a few mods were added. we all know what kind of power our cars should be making with some basic mods but a dyno is a beating the car does not need to take just to make some numbers. the kind of dyno has a lot to do with what numbers you actually get on the dyno sheet. it is well known that a dynojet dyno normally gives you higher numbers than a mustang dyno for example.

when I modded and tuned my supercharged c5 i had it tuned at a shop with a mustang dyno and it read 505 horse to the wheels. I drove across the street to business that had a dynojet and it registred 545 rwhp. during the tuning of my car on the mustang dyno, it registered 525 rwhp and then melted and shot the stuffing of the cats through the exhaust pipes!!! i kept the chunks of filler. I had the cats gutted and tuned it to a safe 505 rwhp on mustang which was 545 on dynojet. This is something I would not do on a regular basis at all. It is a torture test for sure. Cars have lost many engines on dyno runs. caveat emptor.

ed ramos #3028

[KFoster]

I've put a bunch on the dyno. I was one of the earliest ProCharger distributers. They used a Kawasaki street bike engine to run a fan, 650cc I believe. They said it would simulate around 30mph across the intercooler. Saying that to show how much power you need to simulate a driving condition when it comes to moving air. You definitely need an assist as the factory fans on most cars help at idle and low speed, but when you are at WOT without running 50 or 60mph you don't have much cooling effect for the engine. Here at work, I was a QE over the dynos and you run WOT for hours on end. Takes a lot of cooling to support that. For the few seconds you are running on a chassis dyno, you will be OK with a nice shop fan or two. Limit your back to back runs without cool down. You may want to know hp after heat soak, but I would limit that to maybe once when you have your final tune where you want it.

As far as dynos go, I have heard good things about both. I have only used the dynojet for a chassis dyno, but it was what was available. It does read a little higher and is a little more accurate the closer to sea level than it would be at altitude. The smaller the correction factor the better. Biggest thing I can recommend is to use the same dyno. Lets say you used the mustang dyno then changed exhaust and went to the dynojet and thought you gained 50hp when it is just the dyno. It happens. If you go to a dyno day and just want to run your car, have at it, just don't get your feelings hurt or think something is wrong with your car or dyno.

[Bob Eyres]

I've only had my car on a dyno once in the past twenty two years that I've owned it, and the results were unimpressive. But I've seen a careful tuning of modified LT5's a couple of times, and it was a phenomenal improvement in overall performance.
From what I've observed, a good tuner can tweak more performance out of an LT5, in a half day of tuning, than any one modification available. And when many small mods are made, headers, intake improvements, etc., dyno tuning is essential to get the best response from what you've paid for.

I don't quite understand the concern stated above about blowing up your ZR-1 on the dyno..you've got to be kidding. To me, a dyno run is no more destructive to a relatively stock LT5 engine that a spirited run through the gears (to redline) on your favorite "exercise " road. And that happens to my car virtually every time out.
And remember the GM test cycle that LT5's were exposed to. Constantly running a motor from torque peak to redline, and back, over a long period of time. Then a teardown that showed virtually NO wear.
I think some folks have watched too many episodes of "Street Outlaws", where engines are run on the ragged edge of detonation every time out

The best dyno I've seen is the drag strip. Your trap speed is a practical demo of actual applicable horsepower. I figured, (and I could be wrong), that my 117mph trap speed was equal to about 420hp. at the crank. And that's pretty solid for a stock 375hp. LT5 with no internal mods whatsoever. Bone stock except for exhaust.

[Bob Eyres]

I've only had my car on a dyno once in the past twenty two years that I've owned it, and the results were unimpressive. But I've seen a careful tuning of modified LT5's a couple of times, and it was a phenomenal improvement in overall performance.
From what I've observed, a good tuner can tweak more performance out of an LT5, in a half day of tuning, than any one modification available. And when many small mods are made, headers, intake improvements, etc., dyno tuning is essential to get the best response from what you've paid for.

I don't quite understand the concern stated above about blowing up your ZR-1 on the dyno..you've got to be kidding. To me, a dyno run is no more destructive to a relatively stock LT5 engine that a spirited run through the gears (to redline) on your favorite "exercise " road. And that happens to my car virtually every time out.
And remember the GM test cycle that LT5's were exposed to. Constantly running a motor from torque peak to redline, and back, over a long period of time. Then a teardown that showed virtually NO wear.
I think some folks have watched too many episodes of "Street Outlaws", where engines are run on the ragged edge of detonation every time out

The best dyno I've seen is the drag strip. Your trap speed is a practical demo of actual applicable horsepower. I figured, (and I could be wrong), that my 117mph trap speed was equal to about 420hp. at the crank. And that's pretty solid for a stock 375hp. LT5 with no internal mods whatsoever. Bone stock except for exhaust.

[Vette73]

Originally Posted by Bob Eyres

I've only had my car on a dyno once in the past twenty two years that I've owned it, and the results were unimpressive. But I've seen a careful tuning of modified LT5's a couple of times, and it was a phenomenal improvement in overall performance.
From what I've observed, a good tuner can tweak more performance out of an LT5, in a half day of tuning, than any one modification available. And when many small mods are made, headers, intake improvements, etc., dyno tuning is essential to get the best response from what you've paid for.

I don't quite understand the concern stated above about blowing up your ZR-1 on the dyno..you've got to be kidding. To me, a dyno run is no more destructive to a relatively stock LT5 engine that a spirited run through the gears (to redline) on your favorite "exercise " road. And that happens to my car virtually every time out.
And remember the GM test cycle that LT5's were exposed to. Constantly running a motor from torque peak to redline, and back, over a long period of time. Then a teardown that showed virtually NO wear.
I think some folks have watched too many episodes of "Street Outlaws", where engines are run on the ragged edge of detonation every time out

The best dyno I've seen is the drag strip. Your trap speed is a practical demo of actual applicable horsepower. I figured, (and I could be wrong), that my 117mph trap speed was equal to about 420hp. at the crank. And that's pretty solid for a stock 375hp. LT5 with no internal mods whatsoever. Bone stock except for exhaust.

Sounds good...
I'm not a big dyno guy either....To me it's more important for seat of the pants feel than just high numbers...Yes, in the hands of a good mechanic ( one who actually wants to spend some time with it) can use the dyno for opt performance..

I myself put my car on the dyno because I was having a very slight hesitation at around 3,000 rpm under hard acceleration..
When it ran on the dyno all the figures looked good and my guy couldn't pick up the hesitation...Next day I changed out my ignition wires because plain and simple I have had the car for over a year and they just looked old...When I ported the plenum, I pulled the wires from my coils just to inspect and I wound up changing the coils because the contacts were all rusted..Didn't bother swapping out the wires....Picked up a nice new set of AC delcos from a member months previous..So, psyched myself up again to pull the plenum for the third time in six months and did it..
Took the car out for a spin, got it warm and no hesitation...Maybe a little too early to tell but the car ran really good...