The local Import Tuner shop that did my Subaru WRX "makeover" last year has a chassis dyno. That got me wondering about whether it would be a benefit to strap The MoPig (once running, obviously) down on it to see how it performs, maybe get some baseline air-fuel curve #s, etc.

Their shop foreman runs an Outlaw 10.5" Chebby, so it's not like they don't know what a carbureted American V8 is. Also, they seemed pretty interested in having my car on their chassis dyno after showing me videos of a 700+ RWHP modified supercharged Shelby 'stang on it.

So, who here has used a chassis dyno and did it really help w/ getting your tune dialed in? Or should I save the $$$ for test & tune entry fees at the track and dial it in the old fashioned way?

Usually the track is too crowded to make enough passes to try different things to see what works best. So the dyno makes much more sense for tuning experimentation. You can see immediately what helps and what hurts without some of the inconsistencies that happen at the track if you are strictly comparing timeslips. The wideband and graphing capabilities on the dyno help a ton.

The dyno has also helped me diagnose transmission problems correctly when I couldn't really pin down the problems at the track.

Imagine what this felt like? hehehe



You will still need to play with things like launch rpm and tire pressures at the track - but at least you can already be done tweaking things on the engine.

Those graphs look like my 5-year old daughter drew 'em.

I don't understand how the data can do things like that on a legit pull.

This is not a dragracer, but just a dailydriver which I tuned for 1.5 year by ear, buttdyno, vacuum- and AFR-gauge.

I went to the dyno just to get a baseline HP-number and to see what the low cr 318 still put out.
At the location after the first run the shop-owner asked if I wanted to try something on the engine to see if there's more in it.
I didn't bring anything useful but I decided to try some minute changes in timing and mixture adjustments.

All the changes I did during the 5 consecutive runs made the engine put out less HP then the first run...
Was nice to find out I have a well calibrated buttdyno...!


This reply is of not much use in a racecar but just felt like sharing anyway...

The transmission was slipping in and out - so when the rpms fluctuated vs the load it went all crazy. It felt like a bucking bronco from the driver's seat. A straight engine rpm vs dyno roller speed graph showed it pretty clearly.

I did a lot of chassis dyno work a few years ago. In fact, for a while I had a standing Friday morning date at the dyno shop. I eventually ran out of money but it was fun while it lasted.

I swapped intakes, carbs, air cleaners, ignitions, etc. on the dyno. We played with tire pressure and tire size and other things. I did several different cam swaps between dyno dates and generally tested a ton of combos.

I like the chassis dyno but there are a lot more variables than an engine dyno so you have to be careful about what you're testing. My car has a manual trans (Doug Nash 5 speed) so the tests were consistent and fairly easy to understand.

I used to run a chassis dyno and it did help with tuning but depending on the style, it can cause other issues. If it's a brake style then it'll work just fine for tuning, but if it's an inertia style then the engine will think the car is only as heavy as the drum the wheels are spinning. So if you have a hesitation while driving but tune it out on an inertia style dyno, it'll probably still be there when you take it out on the street. It really helps to have some sort of O2 reader to tie into it though I didn't always use that and would just make back to back tests after changing timing or jetting. Always go richer first (if there's no O2 sensor) and lower the timing first as this can prevent damage if you're borderline to start with.

Their dyno does have an air-fuel meter setup, but they can also weld in the bungs I have to test out my LM-1.

For me, the basics (timing, carb tuning) are the primary areas of interest, since I know that there are so many other things that require on-track testing to figure out.

Since it's a new top-end & cam combination on top of a freshened bottom end, I don't know what to expect from it compared to the old combination. I was thinking that having at least some baseline tune before hitting the track could be a time saver...

i did, had the A/F perfect on the dyno. got to the track and it was almost a second slower. leaned it out and went back to where we were.

we take our dirt car to WILLY'S carb & dino before we ever race each year,when he's done theres not 1/10 hp that your combo can produce left in your car, i hily recomend him & getting it done

I had my truck intially tuned "on the street" to get a baseline. Of course, on the street you can't get too much speed, etc., so we finished on the dyno. That got us pretty close where the fine-tuning was done at the track.

"BigBlockMopar "
Did the Dyno you used have a roof leak?

Mike

I chassis dyno lots of cars but you guys can keep your AF meters i pull plugs.

I have been on a dyno twice... once was on Woodward
ave. for a demo run for show and tell... my car got
rained on sitting on my open trailer out there and it
poured water in my dist... I didnt know this untill
after I was up past 4000 rpm and it started breaking
up... then I went on Jakes dyno a few weeks later just
for kicks to see what it made

Anyone tune nos on a chassis dyno? Not fine tune but to check basic function of a system?

Sorry to highjack but while where on the subject.
I know of a chassie dyno pretty close to me and not very expensive but...
The guy have not lowered the rollers into the floor. So the car would be very tilted forward.
Would that effevt the carb in abad way???
I belive so cause the float levels would be very off.
What do you guys think???

No one???