IDI diesel powerband manipulation
IDI diesel powerband manipulation
(OP)
My vintage 1985 Toyota turbo diesel needs more "top end" horsepower, the turbo comes in strong at 2200 revs, and power builds to around 3000 revs and then......nothing !Just a slow trip to the 4000 rev redline. After various attempts to shift the torque peak higher I'm getting a bit frustrated and impatient. So far I've ported the turbo wastegate and freed up the exhaust flow, retarded the camshaft timing(5 deg.), played with various inlet tract lengths, and made adjustments to the injection pump timing and mixture curve. Although some improvement was seen, I want more! I recently fitted a small engine driven blower in place of the turbo, and have picked up power right through the range, however I still need more power from 3-4000 revs (for overtaking on the hyway). The head on these engines is a bit prone to cracking in between the inlet and exhaust valves, so I don't want to risk installing larger inlet valves. I think that the injection pump is the place to look, has anyone had any hands on with the bosch rotary pump? or am I missing something else that is possibly limiting the top end output?...In factory turbo form these engines only put out about 40 k.w. at the rear wheels, need I say more?





RE: IDI diesel powerband manipulation
RE: IDI diesel powerband manipulation
They just are.
RE: IDI diesel powerband manipulation
Port the head.
Install higher lift longer duration cam.
Advance injection timing?
Fit bigger turbo.
Fit bigger less restrictive exhaust especially after the turbo.
Don't bother with tuned length.
Increase boost and fuel to match.
Regards
Pat
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RE: IDI diesel powerband manipulation
Measure EGT's.
RE: IDI diesel powerband manipulation
Installing an intercooler on a turbo engine that doesn't have one, will make a big difference. It will not make any more power automatically, though - but it will let you increase the fuel delivery from the pump.
RE: IDI diesel powerband manipulation
RE: IDI diesel powerband manipulation
Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
RE: IDI diesel powerband manipulation
Yes Pat, down southern Vic. on the great dividing range, 600m. above sea level. While we're talking cold, does air have a lineary expansion rate, if so then why does my diesel engine feel so much stronger on a cold evening?.... wouldn't that indicate unburnt fuel going out the exhaust when the engine is inducting warmer air, through a lack of sufficient oxygen to burn the injected fuel? (this engine has no temperature sensors to adjust mixture/timing).
RE: IDI diesel powerband manipulation
Anything like even a slightly "sporty" cam will drop the cylinder pressure to the point where the engine will be impossible to start or run at low RPM.
Presumably a continuously variable duration system (where the duration increases with RPM) would cure this problem.
Even with such a system the slow rate of burning would probably limit the high RPM power.
The only practical method of really raising a diesel's performance is to increase the boost pressure.
RE: IDI diesel powerband manipulation
RE: IDI diesel powerband manipulation
Depends on the application, but the governor springs are attached to the mechanism attached to the main throttle lever inside the pump. Some applications dont have a separate idle spring. When the flyweights move, they compress the springs in order of rate, if you have 3 springs, the softest is idle.
Perhaps what you feel with the advanced timing is the fuel drop off more quickly, rather than an actual top-end reduction in power? Are you rotating the pump the right way? Does it get very noisy at idle with it advanced?
The screw and locknut on the side of the pump with the delivery lines is the main fuelling adjustment, not timing related. It is just moving the main fuel lever start point inside the pump, a fuel offset if you like.
Best get freindly with the pump. They are little works of art, very satisfying to tune when you understand what each part/adjustment does. They share a common body, so parts such as camplates and plungers are usually interchangable, and cheap these days. You could also of course change to a much larger pump that has a simlar nose diamter and taper and start from there if you really want. The Cummins 4BT pumps are particularly well regarded.
The manual is here, enjoy:http://www.htsuk.plus.com/BOSCH_VE_PUMPS.pdf
(Hope it is OK to paste this link)
RE: IDI diesel powerband manipulation