A few of you might have seen in my project thread but the race car's engine is quite down on power and is generally having a few issues. For background, it's spec is:

Pocketed pistons
BP260H cams
45mm Omex bodies (not Jenvey copies)
Satchell inlet
Longmans P&P head
Standard exhaust manifold with Piper back and middle box, no cat
Wasted spark with HT leads and NGK BKR6EK plugs

When the car was first mapped it made 183bhp at the hubs which was a reasonable amount. Over the course of last season we've felt it was getting slower in a straight line and this was backed up by it making 157bhp at the hubs last weekend, quite a drop! It was the same dyno and the same guy that did both runs and the mapping itself so hopefully fairly consistent. The biggest difference between the two runs was outside temp, it was about 2 degrees last year and 30 degrees this year, although the dyno is supposed to account for that.

The mapper said this year that the car was running a bit rich compared to what he expected and suggested it could be cam timing or exhaust system failing. Cam timing is pretty easy to check so I'll get round to that. The exhaust sounds the same so I'm not sure on what else I can do to see if it's falling apart?

The other issue I'm having is when hot (i.e. just after a session) the car will splutter and not idle at all. On rev it's ok but is quite brutal transitioning from 0 throttle to a small amount (car lurches when throttle kicks in). It will also "hunt" a bit but I can see the throttle %age changing even with my foot off the pedal. I think most of these are related a dodgy TPS so I'll try a new one of those to see if it fixes it.

Summary:

- Down on power significantly and running rich
- Cam timing?
- Broken exhaust?
- Dying after track session and very rough off - on throttle transition
- Broken TPS?

Any ideas or anything anyone else can think of?

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Rallye Race Car

I`ve had this turned out to be a broken wire for the tps

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basically I lost the pink wire iirc which lost me my modulation.

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Pressure is fine, I have a fuel pressure sensor and it consistently reads 3.5 bar

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Rallye Race Car

I appreciate it! Little p**sed off it's lost power after all the money I've spent but it was my first go at building an engine so not massively surprising.

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Rallye Race Car

Plugs were quite black last time I took them out. Do you have any recommended alternatives? I'm not that clued up on heat ranges etc.

Sam (the mapper) said something along the lines of the lambda not doing much on the car so maybe that's because as you say, the narrowband isn't much use to the Omex. Presumably though if I change lambda I'll need to have it remapped?

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Rallye Race Car

I've had 2 mapping sessions (due to manifold change) and each cost me £600, how does Sandy compare to that?

I've thought about going to Track and Road in Essex as they've got a reasonable reputation? Part of me things if I'm going to have another mapping session it would be worth doing a couple of other changes as well (slightly bigger injectors, swirl pot fuel system, maybe new exhaust as well)

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Rallye Race Car

Don't even go there, I'm still annoyed about it!

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Rallye Race Car

Is that per day? Hoping not per hour

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Rallye Race Car

Only a 4.5 hour drive from the workshop!

Not sure how similar the spec is but it's fairly generic. The P&P head is perhaps the biggest variable as it wasn't done by him so is a little unknown.

I've got an external FPR, if I get a wideband lambda that could make things easier, taking the bumper off is a 2 minute job!

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Rallye Race Car

Had a look over some stuff today and found a few issues.

Compression was (from L-R as I look at the engine, in bar): 12 - 10.5 - 12.5 - 12 so not great!

Plugs were also not in a great state:



Finally the exhaust cam was out of time a bit. I'm going to buy a proper locking kit rather than the drill bits you see here as I tried to re-time it today but it moved again for some reason. Clearly I'm doing something wrong so will give it another shot with a proper kit.

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Rallye Race Car

Yea, I'm guessing I'll need to have someone tweak the map, more money to spend!

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Rallye Race Car

Probably! It needs to survive 2 more races before I can strip it down. If it's buggered, I'll need to think about a new bottom end

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Rallye Race Car