Aftermarket Turbos. Over injection at low boost?

Submitted: Thursday, Jan 22, 2004 at 14:18
ThreadID: 9950 Views:2112 Replies:2 FollowUps:0
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Just wondering.
How do aftermarket diesel turbo conversions avoid over injecting fuel at low RPM/low boost pressure? I would imagine if the injection pump is set to give an appropriate maximum injection volume at normal boost then it would be far too much at low revs and result in much black smoke and oil resultant contamination.

My factory turbo(Mazda Bravo TD) appears to use the boost pressure to control the maximum injection volume but I don't imagine this is available on pumps designed for non turbo use.
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Reply By: howesy - Thursday, Jan 22, 2004 at 17:05

Thursday, Jan 22, 2004 at 17:05
In older models such as the 2.8 hilux this is indeed a problem but not where it is a major one . it is for this reason that I tell people to fork out extra cash and get thepump taken off and stripped and cleaned and recalibrated for the turbo as this also changes the static and auto advance settings to better suit the turbo. It cost a lot but the fitment of a HAC unit drastically relieves this problem also
AnswerID: 43994

Reply By: prado95 - Friday, Jan 23, 2004 at 12:36

Friday, Jan 23, 2004 at 12:36
Phil, your assumption is on the mark.

Its not uncommon for the fuel load to be set such that either the performance is reduced from that available, or excessive such that there's a lot of black smoke (& high EGT = BANG! engine buggered). Since the fuel load is non-linear (as revs & boost build) a non-linear fuel load is required in order to achieve acceptable & safe power.

Dispite the postings of some diesel shops and the cost of the compensator, its a worth while addition if longivity i& decent performance is of any consequence. As pointed out above, almost all factory wastegated turbo diesel engines have one fitted as standard these days (either a mechanical or electronical sensor & interface to th ECU). If its fitted & correctly adjusted it will also assist fuel economy & save the ozone layer some.

Electronically controlled diesels tend to measure the boost (amongst other things) and make the appropriate adjustements to the fuel load to avoid overfuelling.

All this assumes that the injection pump & injectors are in good condition. This is the first step, along with a decent free flowing exhaust. In fact the exhaust & injetcor service might be sufficent for your needs (you did not mention any particular vehicle). Full benifets of the turbo can then be realised.

AnswerID: 44099

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