Following the RR day and the disapointment I had suffered (well documented elsewhere)I contacted 3 other rolling road companies.All three confirmed the incorrect method that was used on the day for the auto`s and hence I do feel vidicated somewhat. However having been contacted by a forth operator tonight I am sure the information he provided me is gonna shock you. I have quoted him below and he clearly stated that the only true way to get an uncorrupted bhp figure is in a transmitted gear as close to 1:1 ratio as possible, and that any deviation from this leads to either artificialy low or high figures.So you ask why the problem? well guys the arse operator tested the manuals in 3rd gear? and as the third gear of a manual transmission is 1.302:1 the bhp figures were wrong and were overstated,the correct gear should of been 4th which is exactly 1:1 and interestingly the 3rd gear in auto is 1:1 and forth is 0.694 :1 the figures again were wrong and UNDERSTATED!!! A little bit of maths here clearly indicates the WHOLE days testing of ALL the cars was wrong and now I think we should seriously consider that the guy was a major ARSE and will hamper any tuning before and after as the figures were ALL corrupted.If the guy had actually provided receipts for the work I am sure it would not be inconcievable to suggest to him that he had infringed trade description act!

Trust me guys this is not sour grapes it has become an important issue, just as much to you guys with big bhp figures as well as the disapointed guys.

I for one will be contacting them for a refund as they did not perform the service they said they would ie a maximum power run.

 

Jeff TT

 

GMC Motorsport

An important part of when a test is being done is that the same gear is always used and the correct one. This is probably the most important factor to remember, especially if you are having a before and after conversion test. The reason this is so important is down to the basic physics of gear ratios. Why does a car accelerate faster in first gear than top gear, after all the engine is still the delivering the same power? The answer lies in the gear ratio. If your first gear has ratio of 4 to 1 and top gear is 1 to 1 it will accelerate (theoretically, but not in practice due to extra friction in lower gears) 4 times as quickly because the effect is to give your engine 4 times the power. This ratio difference has the same effect on the horsepower registered on the dyno. It is normal to a test a car on a dyno in as near as a 1 to 1 ratio as possible so you get the truest horsepower reading you can. This is often difficult with modern cars as no gear is a straight 1 to 1. Most 5 speed gearboxes have a 4th gear at say 1.3 to 1 and 5th gear at .93 to 1, meaning that in 4th gear it will overstate the horsepower and 5th understate it. If we take this to is logical conclusion a car first tested in 5th gear and giving a 100 horsepower at the wheels with a .93 tol ratio is really 107 BHP whereas if the vehicle is then tested in 4th gear with a 1.3 to 1 ratio the horsepower reading will be 100x1.3 = 130 BHP. These are hypothetical figures, as the friction, and hence horsepower losses, in the gearbox are greater the further you go way from 1 to 1, but the principle is still the same. So be quite sure that every time your car is on the dyno the same gear is always used.

 

 

Originally posted by Jeff TT:

So you ask why the problem? well guys the arse operator tested the manuals in 3rd gear?

 

 

My dyno sheet says 4th, but I didn't actually see which gear was used?

mine was tested in fourth as i watched as he changed up through the box before the final boot. as he did with all i watched. also dyno sheet states this was tested in fourth. warren please varify this by ringing the tester. i dont doubt that he did the autos wrong though but leave us manual boys out of it...."T"

just a quick question jeff.

Did anyone bother to mention to him before he ran it that maby the jap sepc was different to the uk spec. with regards to the box.

i dont kwow cause i drive a manual.

But you are making a bigger thing out of this than i make out of SE.

Not trying to upset anyone at all just asking.

Mine was tested in 4th too.

It says on the sheet and recorded 133mph on the speed thingy. I've only managed 103 in 3rd and that's at about 8K.

 

------------------

Jezz Palmer.

Grey '92 S13, S14 T28, SAAB FMIC, SE Stage 2, Cybercraft Induction Kit, Blitz FATT-S.

217.7 RWBHP ~ 13.5psi @ RARE

mine was tested in 4th also, as i saw it for myself.

 

as warren says, if the guy didn't know about the auto box hold feature then someone could have told him...

 

i think they mostly test their race cars there, is that right warren ? in which case, they probably dont have much experience with autos, period. there are not many full auto race cars....

 

one of the guys even said to me that they only use the dyno for the public when out of race season, or nearing the end of the season.

 

But you are making a bigger thing out of this than i make out of SE.

Not trying to upset anyone at all just asking.[/b]

 

 

He He Warren Are you sure about that mate?

 

 

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Jeff,

My car was tested in 3rd which is what I expected. Yours would have changed up into 3rd, so the peak figure is still right, but the curve itself is confusing. Of course the torque plot will be a waste of time though.

Mine was in fourth.

 

And what do you mean Warren by "theres more to my car than meets the eye"??

 

It's been to S.E. dont you know. ;-)

 

No seriously the mods on my car are exactly as I said before. Exhaust, SE Boost Upgrade and Intake. Lots of TLC

 

Grant

thanks grant everyone was under the impression it was just exhaust and intake.

 

What boost are you runnign if you dont mind me asking.

Well I was told by a 20year established rolling road company,that you can't get a true figure from an auto,but before I knew this,I booked in a session on the rollers 0ne week in advance,When I get there we drive the car on the rolling road the guy lifts the bonnet connects it all up,gets into the drivers seat and says O SHIT!Sorry I can't do it it's an auto!

Give them a call and see for yourself.tel 01759373399.

 

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My auto was tested in 3rd as it should be. I did take the time to show him about the overdrive button (I was the first auto to be tested). Of course, I dont have a hold button being a UK car so my graphs show 2nd gear and then into 3rd gear. Just ignore the second gear bit.

 

Jeff, if yours was tested in 4th, can't you apply the maths that the guy you quoted in your first post said and adjust that way? Are you saying that the guy didn't even press the overdrive button to turn it off? My boost controller isn't fitted correctly so I could only do runs at safety boost and stock boost and I got exactly the hp figures I expected (my torque was a bit higher than I expected).

 

Andy

I don't know, I just take it in to SE talk to Dave and ask him to set it up to the maximum output for everyday use. I'll ask SE tomorrow.

 

I am sure they will be pleasantly surprised, but when I took it in there about 1 month ago Dave said to me that he felt my car was very strong for the mods I had and very few 300's feel as strong.

 

Grant

Originally posted by Grant:

I don't know, I just take it in to SE talk to Dave and ask him to set it up to the maximum output for everyday use. I'll ask SE tomorrow.

 

I am sure they will be pleasantly surprised, but when I took it in there about 1 month ago Dave said to me that he felt my car was very strong for the mods I had and very few 300's feel as strong.

 

Grant

 

 

Sorry...talking about the level of boost.

 

It will between 12.5 and 14.5psi, Think we can assume that yours is on the high side !

Ok ok seems I made an arse of myself now, I misunderstood and thought third gear was used in the manuals as well,but then I am man enough to admit when i make a mistake and appologise for that. Jeff TT

 

According to my sources, 4th gear Manual ratio is 1:1 and 3rd gear Auto is 1:1

 

 

Checked with SE.

 

I am running 1Bar = 14P.S.I

 

Dave reckons that I could get it up to 400BHP with one of their chips. He said that UK manuals always feel the most powerful.

 

I think the next step for me will be a bigger intercooler. A friend of mine has had one made for his RS Turbo with very positive results. He ran a 15 second 1/4 mile at 16P.S.I and no other mods.

 

He reckons (yet to be confirmed) that the guy makes them made for a couple of hundred quid.

 

Does anybody know the specs and sizes of something like the HKS or the really big Stillen one?

 

I could get a price and see if we can do a group buy.

 

Grant