I Got my '90 3rd-Gen Dynoed

I am an intern (well, on Saturdays at least) at MAC Autosport in Parker, CO, so every time I get a new vehicle, I get the itch to do a couple of dyno runs to see how it runs.

I had the privilege of running my 1990 VFR750F a couple of times on their DynoJet.

I was (very) pleasantly surprised!

I put down 84.39hp/47.96ft-lbs with an SAE correction factor of 1.23 (they have a digital "weather station" that calculates it -- you can't change it; the conditions were: 73.85F, 9% relative humidity, 24.41 in-Hg absolute atmospheric pressure, and the Dyno is at an elevation of around 6,100ft above sea level -- thanks kennybobby; I forgot to put this in).

The air/fuel curve was very nice -- an average AFR of 12.38 (it went a little bit rich up top, but not excessively)

Here's the sheet (I had to install WinPEP on my laptop to convert it to a high-res jpeg, as the dyno computer at MAC doesn't have a virtual PDF printer driver installed):



Now, thanks to tinkerinWstuff, I was able to calculate the mean drivetrain loss of a 3rd-gen VFR (16.715%).

Under ideal conditions, our 3rd-gens are supposed to put down 98.5hp @ 9700RPM and 53.9ft-lbs at 9000RPM.

My peak numbers were at 9750RPM for power (almost exactly the same rev-location as stock), and at 7590RPM for torque (a lot lower in RPM's than "stock").

Now, from this, I calculated that my bike theoretically put down 101.33hp/57.58ft-lbs at the flywheel.




Now, for some useless information!

Here's a comparison between the acceleration (mi/hr/sec) of a 285hp Subaru Legacy GT and our tiny (well, tiny and heavy) VFR's:



So, basically, for an older, carburated bike, we're not doing bad at all!

 

That is great--thanks for sharing.

What is your elevation there?

What jetting do you have--is it stock or has it been leaned out for the thinner air?

It would be interesting to see if leaning it out slightly would increase the torque and power numbers.

It looks like the first torque peak was around 7500 which happened right after the A/F ratio peaked leaner at ~7200. Then there was a second torque /power peak at 9700 when it was slightly richer and running out of air toward the end (volumetric efficiency dropping off).

i just love riding that broad flat torque curve 6 to 10 is fine...


p.s. how did you flatulate the drive-train losses?

 

Stock or modded?

 

Bone stock, as far as I can tell (the previous owner "cleaned" the jets -- whether or not that means that my bike now has been re-jetted, I have no idea).

I have the stock exhaust (headers-back), and I haven't seen my air filter to see if it is high-flow (the previous owner just replaced it, but with what, I have no idea).

Not that it matters, but I run Mobil-1 Full Synthetic.

The bike has been adjusted for high-altitude.

With regard to the altitude of the Dyno -- MAC Autosport is at roughly 6100ft above sea-level.

I have thought about leaning it out a little bit, but that's a lot of work to re-jet the carbs, and it may or may not actually do anything.

If you all think it would be worth it, I might give it a go...what size jets would you suggest?


Edit:

Woops...forgot about the drivetrain loss. Simple relative error calculation based on the brake-horsepower and flywheel torque numbers from the factory specs and tinkerinWstuff's last dyno.

I also did some research for the average drivetrain loss for a bike (for an AWD m/t car, it can be from 20-25%, for a FWD/RWD m/t car, around 15-20, and for an automatic, 25+%), but from what I have found for the average chain-driven, wet-clutch bike, it's around 12-18% (most of the numbers I have found were around 15%).

As we all know, tire pressure, tire compound, chain and clutch wear, etc. will have profound effects on this, so it is still an estimate unless you do a clutch-in, in-gear coast on the dyno rollers.

Thanks!

 

If it has been adjusted for high alfitude then the jetting will likely have been modified, e.g. pilot jets, main jets and needles/position of needles.

If you ever open the carbs be sure to write it all down and post it.

 

Cool, I live in Denver as well, I calculate that the HP drop is about 2% per thousand foot. So you might be putting down at sea level about 94 RWHP. I had my 1997 VFR dyno-ed and the carbs tweaked by Mike V from Brothers Honda in Bremerton Wa when I first bought it in 1997. It dyno-ed at about the same as yours, he said it was a strong engine, then three months later I was t-boned by a Coca-Cola truck and the bike was totaled. I liked that bike....

577nitro