bfnnrgn

Took my stock SL65 to the dyno today. No tach pickup so no TQ reading. 3rd gear pull due to speed limiter. 76 degrees and it was raining out so humidty was very high. It still put out a respectable 530 rwhp.

JAYCL600

strong numbers!!

bfnnrgn

I know, I can't wait to see what it'll do with a tune.

NSM

Very strong....

TMC M5

530rwhp is a strong run!

Tom

Addicted2Speed

That's very strong! What year SL65?

bfnnrgn

Thanks. It's an 06.

I think the highest stock dyno of a 65 was 540 if I recall, but no idea of the conditions it was ran in. Maybe if it wasn't raining out yesterday...

Marcus Frost

bf,

What kind of dyno? Do you have a scan of the chart? 530rwhp is awfully high for a 65.

Unfortunately, without tach pickup I'm always a bit wary of the validity of the numbers.

-m

bfnnrgn

Yeah, the graph is in the car. I'll go get it. For comparison a M5 with a Dinan stroker motor, full exhaust, and intake ran right after me and put down 524.

Ok here's the chart. I hadn't looked at it before. It's actually 528 rwhp. The operator must have rounded up when he told me 530. Close enough.

Murtaza

Wow nice numbers!

Was that Darrens M5, that thing is fast

TMC M5

Are you the SL65 that Darren was supposed to run in his Dinan Stroker? Did that ever happen?

Tom

TMC M5

I tend to agree...but these cars are extremely hard to pick up the tach signal on a dynojet. I tried printing out some instructions on here and trying it last time I dynoed....but it just didn't work. It looks like an optical pick-up is the way to go....but it isn't an exact science either and it takes alot more time.

The stongest stock 65 is by a member on here. However, I kind of question the dyno/operators with a 550+rwhp pull ...can you see what looks odd in the attached dyno chart?

Tom

bfnnrgn

Yes, thats Darren's M5 and yes that's my SL65 he's referring to. He's having some issues still and he doesn't believe he's making the power he should be. We raced when he first got it and I pulled him hard, worse than his previous silver M5. He went back and had the intake problem addressed and we were going to race Sat but I wasn't available. We did 3 runs yesterday after the dyno and I pulled him all 3 times, though not as much as the first time we raced, starting at different speeds up to 140ish. He's still investigating the issue. He data logged the runs. He thinks it may be a tank of bad gas.

bfnnrgn

For starters the TQ should be much much higher.

Murtaza

Torque, rev limiter past 6.5k...

TMC M5

Totally agree...the problem is that the RPM's are completely skewed...when was the last time you took your SL65 to 6,750RPM? By skewing the RPM up in the scale the torque is undervalued.

TQ = (5252 X HP)/RPM

Usually our cars are having fits by 6,000 RPM. The additional 750 RPM represents a 12.5% increase. So the torque is reading probably 12.5% low. That assumes a third gear dyno where the car would be able to go to redline. If it was a 4th gear dyno...the numbers would be even more skewed as the car would hit the 155mph limiter at around 5,300RPM. Who knows what actually happened...but I would have questioned the dyno operator given all the discrepancies.

Tom

jmf003

For what its worth most (maybe all?) dynos measure torque and then compute horsepower based on torque and RPMs. It'd be pretty hard to measure horsepower directly.

Wikipedia's explanation on how it all works is pretty decent: http://en.wikipedia.org/wiki/Dyno

If the RPMs aren't correct it's the horsepower numbers that are likely to be incorrect. The torque numbers should be correct, although the RPM scale would be wrong.

Marcus Frost

There are a number of ways dynamometers try to compensate for the lack of an RPM signal, but just as jmf said - horsepower is a function or torque, not the other way around. I won't say your car isn't powerful bf, but you simply cannot use this graph in any sort of comparison with other members charts on here who've used an actual RPM signal on their charts, no can you use it against the M5 you dyno'd with if he had an RPM signal.

The only thing I think your dyno is good for, is to tell you there is isn't something drastically wrong with your car, but honestly you'd butt dyno could probably tell you as much

I've said a million times on these forums, if you guys want to dyno your car, do it with someone who does MBs, and KNOWS what to do. Don't expect to be able to print out instructions and guide them through it, cause it doesn't work. Additionally, even if he gets a clean run, you won't have any other MBs to compare to from that dyno.

I have dyno'd all of my MBs at the same shop, and they've done dozens of various MBs there, so there's a great database of cars to compare mine too to see how it stacks up. This is extremely useful in the event that something doesn't smell right, because you've got the data right there to compare it to. Don't assume you can compare a Dynojet in NYC to a Dynojet in LA. The best place to do comparisons is from the same exact dyno in the same exact place.

-m

V12Godspeed

I could show you one with 542RWHP, Stock...and another one of 560RWHP with a bit of Iceeeeeeeee....lol!

bfnnrgn

This would have to mean that either:
1. My car is making more power than the dyno shows
2. That the M5 is making less than it shows, making the tach pickup less accurate.

Given the weight and gearing advantage of the M5 over the SL65 and that our dynos showed within 4 HP of each other and the fact that on the street I pulled on him every time right after the dyno was completed it's only logical to conclude that one of those must be true.

Also this shop had dyno'd quite a number of MBs, including the M5 owners MBs. They already knew they couldn't get rpm off the V12 without me telling them and how to operate the vehicle.

V12Godspeed

So you raced the M5? Nice...who won?

Marcus Frost

Not necessarily, especially given the revs the M5 was making. You cannot compare peak hp vs peak hp, especially when the powerbands are completely different as they are with the M5 V10 vs the V12 Biturbo.

I actually would interpret that more along the lines that dynos can be really misleading, not that you were both making similar power. You just indicated before he was having issues, on top of the fact that you did not get a good dyno because of the lack of RPM signal.

They should be able to get an RPM signal off the V12. It's available at multiple sources, and may be a bit time consuming, but it's definitely possible.

-m

bfnnrgn

I did. Which is odd given the dynos and weight differences.

bfnnrgn

It's believed he's having issues based on the results of the dyno and following races. He didn't believe there was an issue going into it.

There wasn't any time where the M5 had an advantage though in any of the races and that's whats confusing. We started the races from 60 except for one which we slowed to 50 I believe. Aside from the initial jump he always got, which I think is because he was giving the GO and I started at ~3000rpm in 3rd and turbo lag I was able to make up the distance and pull ahead by 140 each time. My car pulled harder as the speeds increased which is usually the domain of the M5 and it's closer gearing.

bfnnrgn

I just got back from Darren's house. We didn't run our cars but I did borrow the vbox and did some runs in the same locations he did (in Mexico) and the temperature was the same as well.

Here's the best results of multiple runs. I couldn't get traction at all, I really need to figure out how to launch this thing. But as you can see my 60-130 is smoking. His results are m5board. I don't know if he'll post these results on there as well or not. He's having issues with his car again today so not sure what's going on exactly.

Speed(mph) Time(s)
0-60 04.54
0-100 08.77
60-130 08.62
0-30 02.2

My 50-110 time was 5.64 as well.