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Discussion Starter #1
Right,
I ran the car at the Top Speed Challenge on Sunday.

Didnt do too bad. Qtrs are still rubbish (I need to learn how to launch it still....) and top speed was maxxing out at 156 - even with the "long" track we had later on.

One point of concern was that at approx 5,900 rpm and then at approx 6,300rpm on the last run (according to my unconfirmed accurate revcounter) the engine stuttered. Big time!
Flat out (as you would assume) it was litterally like I lifted off for a split second and then put my foot back in.

Having a few thoughts and chats with mates who run 200's (with little engines;) ) someone mentioned it may me underfuelling.
Now when I had it R'Roaded the first time round with the std intake to turbo piping the operator said it was overfuelling - giving approx 9-10%.

Does anyone think this is a point of concern? It wasnt detting/pinking (I know what this is and have had it previously in the std CA motor) and the motor held together.
I was running std boost (0.7 bar) all day, so I dont think it was the spark blowng out. Could it be the fuel pump running low? (A mate runs up to 350 bhp on the same one - Walbro 190L/hour)

Any thoughts or comments appreciated.

Im gona speak to Mark @ Abbey and maybe get it roaded on their "Roller boxes" :D:D:D

Cheers in advance.....

PS. Dirk. My mate loved the ride in your motor. What bhp is it? I heard about 600. Is that right?
 

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I recall going to help a female friend out one time, her car did this, exactly this but at lower revs, she was low on fuel.

High speed runs and full-on pumping in the fuel tank really needs a 'head' of fuel to ensure constant delivery, with non-race type pumps the lack of 'head' can do this.
 

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Mycroft's got it :)

Probably just the fuel pump not getting enough juice and running a little weak spot in the fuel flow.

Are you running with the stock RB25DET ECU ? As I have heard lots of complaints about an apparent miss at 4.5k-5k rpm. New plugs with tighter gaps usually help this though.
 

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HELLO MATT

NO PROBLEM ABOUT THE LIFT, SORRY I COULDNT SHOW TO FULL MIGHT OF THE CAR AND ONLY A QUARTER MILE, WE RETIRED FROM THE DAY EARLY DUE TO SOME SERIOUS SPEED WOBBLE ISSUES AT 160MPH CAUSED BY A DODGY TYRE WE THINK SO BACKED OFF AND WENT HOME AND LEFT THE SUPRA TO STRETCH ITS LEGS AND TRY FOR MORE SPEED, HOW DID HE GET ON WITH THE LONGER DISTANCE? WHEN I ELFT HE HAD RUN 185MPH, DID HE BETTER THAT?

AS FOR YOUR PROBLEM IT COULD BE ANYTHING OF COURSE BUT DOES SOUND LIKE FUEL DELIVERY WHICH IS CAUSING THE ECU TO BACK OFF OR JUST THAT THE FUEL ISNT THERE, DID YOU HAVE PLENTY IN THE TANK? WE USED TO GET BIG PROBLEMS WITH OUR TT SUPRA WHEN IT WAS LOW ON FUEL, JUST A THOUGHT.

TAKE CARE..
 

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Had a very similar experience with my old merc 300e24, turned out to be the fuel filters restricting flow at very high revs.........
 

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Discussion Starter #8
Cheers guys....

Right, A few people have said fuel pump.
Ive spoken to Mark at Abbey (he rang me! What a guy.....now get me my discs :D) - he says fuel pump too. Looks like I need a GTr one! (Damn it I just sold one!)

He said it may well fuel OK for a R/R run, but given the durations involved at max load, it cant keep the "head" of fuel up, hence probably running a bit lean.....:(. I quote, "Not blowing our own trumpet, but we could test the car for this by holding it at 6,000 rpm". Cheers Mark. Looks like I will do when I come see ya....

In retrospect, I can remember when I upped the boost on the old set-up (CA 1.8l) and the tired old std pump. It would struggle through the revs just like it did on Sunday....

Cheers again. Im gonna get a pump and get Mark to try it on the roller boxes for me. Lets hope I get a few more horses too!

Andy - THe Soup made 187 mph on the last run(s) two up with Keith_C. Hope you get your wobble ;) sorted soon.
 
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