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beepbeep beepbeep is offline
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Join Date: Jun 2001
Location: Sweden
Posts: 5,564
930 never ever had pop-off valves and never suffered from backfire. If they did, you couldn't hear it or intake assembly was much stronger than SC's and thus didn't blow.

As far as I understand, your car is somewhat special case where you have something you call "airbox" which is actually nothing but home-made plenum chamber. For me, "airbox" is assembly containing filter and is situated before CIS and turbocharger. Most factory turbocharged cars have very stong cast "plenum chambers" (=cavities between throttle and heads) and thus are immune to backfire. Yours seems to be built of rectanglular steel sheets?

Typically, if a turbocharged plenum cannot survive occasional "burp", it shouldn't be used on a turbocarged car Also, backfires occur when fuel is poured into stacks w/o any spark to ignite it and shouldn't happend at all.

Anyway, I'm glad that you found the culprit! I still find your boost treshold amazingly high up the revs. Is it some sort of old Ray-Jay turbo you are using? I believe you can make your engine respond much much better if you find the reason of late boost buildup. Is turbo too big? Maybe you have a leak somewhere? Frankly, for your power level a KKK K26 (Audi 200 Turbo, Porsche 944 Turbo) would be a perfect solution! They are plentiful and not expensive.

Regarding water injection: well, it's a working solution but should be regarded as band-aid. It would be pity to destroy the engine if water runs out or the pump stops working Some people have built neat little intercoolers that fit under the duck-wing. Take a look at OEM intercooler from SAAB 900 <92. It's quite might be able to install it. Also, if you are handy you could make water/air system. They are very compact and effective albeit somewhat complicated.

I'm looking forward to seeing AFR and power curves. 250hp from your combo on 6 psi boost is very good! OEM ROW 3.0 930 made 260hp with 0.8 bar. A more responsive turbo and a touch more boost and you will have very driveable and peppy car indeed!

P.S. Personally, I don't think yo should run AFR's richer than 12.2 when on boost. There is mileage and power to be made there.
Thank you for your time,
Old 01-06-2008, 06:52 AM
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