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Engine rebuild and Rolling Road


Paulo

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The reason I dont think EFA has said anything wrong is that I just dont believe power readings on any dyno or RR are particularly accurate. I remember watching my first high power Vx engine on a dyno. It was put through a few power runs and the results varied by over 10BHP. Just letting the thing cool for a minute and doing a power run gave 5BHP more. No doubt a change in ambient temperature or humidity would also make differences. There are so many variables that I personally struggle to attach real significance to the numbers. RR's are by definition even less accurate that dynos as there are even more variables.

 

I have a dyno chart from Swindon showing 249.8BHP and my engine has done about 5 trackdays and very few road miles. It's pretty fresh. A similar (near identical engine to mine) struggled to make 200BHP on a very reputable RR, but both cars feel identical on power and on a long straight, there is nothing between them. The same RR has shown higher power results for cars that I know are alot slower than mine in a straight line. I also know my engine would show lower power on certain dyno's and RR's, and more on others.

 

BHP's and lb/ft's are great for pub banter and a rough estimation of what the engine can do, but I think not much more than that.

 

This does not detract from the great work some of the engine builders we use. It just makes it a bit harder to quantify the results.

 

 

 

Edited by - Alex Wong on 1 Aug 2006 09:17:46

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Alex - the whole point about Track'n'Road's relatively advanced setup *IS* the repeatability. Runs don't vary by more than 1bhp, and it should correct for temp/pressure/tyre slip (a new one) accurately. As has been said, it's repeatable enough for to have OEM customers like Noble & Mosler. Though not good enough for Arnie for sure! An engine's power will vary over the course of the day since it can depend on oil/water temperature etc. Anyway, I think this thread has diverged somewhat. Most of us agree the important thing is how the car drives, and they seem to do a great job there.

 

 

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Surely the whole point about setting the car up on a rolling road is not so much the 'willy waving' Max Power figures but more, as Angus has just done, to end up with something that is good to drive under most if not all conditions the driver will experience on road and/or track.

 

I have never seen the point of of putting a car on a RR simply to get the biggest power figure you possibly can yet it might not actually be pleasurable to drive under normal conditions or may not even get through an MOT. I know some people have done this (naming no names *tongue*) but what is the point if only to use it for boasting at the bar 🤔 *confused*

 

Brent

 

2.3 DURATEC SV Reassuringly Expensive

R 417.39 😬

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Well, getting a max power figure only takes a few runs (unless you're going mad fiddling with cams/induction etc.). The part throttle mapping can take as long as you have (OEM take months!) but you can get very decent results in a day.

 

 

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I think Alex is right about what EFA was saying - he wasn't saying they were bad, just that their claims of repeatability were suspect, or perhaps mis-guided - nothing libilous - however, speaking to Steve he said that yes, on those particular days certain aspects to do with both car and rollers conspired against getting a 'proper' result. Although how one can question a RR and then base ones opinion on a drag strip result with all the variables that includes, is beyond me!!

 

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Hi Paulo

 

Re the engine spec, I have an R300 spec engine and I am interested to know the exact spec of yours, 236bhp is nearer to R500 spec, I thought R300's were around 160bhp. If you get a chance to post the exact spec I would appreciate it. I have never put my car on a rolling road but we copied the R300 spec exactly.

 

Rgds

 

TC

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Tony,

 

Jason langan (Hellier) built the engine,it has a reworked MS2 head with Jason's own cams,omega pistons, roller throttle bodies rebuilt by Minister, a Caterham 4-2-1 exhaust, lightweight flywheel and a MBE remapped by Steve Greenald.

 

regards

 

Paul

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Sorry, if i wasn't clear, it used to be an R300 spec. The change is quite dramatic 😬

 

We could argue for hours about the power recorded, but who cares. It's much too fast enough........

which is the result I was looking for.

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