Just for more info my 96 model 1HD-FT had the ASCD on it when I bought it.
It does not now.
It does not now.
1hd-t vs 1hd-ft injector pump
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So I heard my name mentioned about timing, but im no authority. Working from Dougals advice regarding peak cylinder pressures is why I originally retarded my 3B timing and to my surprise I gain significant lower end torque which I really enjoy. Very improved drivability. I think that the rate at which fuel burns can be influenced by so many variables that to advance your timing to the point at which you completely maximise power you take away your margin of safety for hot weather and hot fuel or high intake temps from running no intercooler or perhaps you try out a new fuel additive that happens to have cetane in it which also speeds your burn. Very easy to get into a situation where you are over advanced and don't know it. Your performance suffers, use more fuel, overheat often, but more importantly your engine experiences much greater peak cylinder pressures and eventually you will break a nice big hard to replace piece of it. Namely your crank shaft. How do you know what to set your timing at? This should be a whole other thread or at the very least a huge part of this thread. Power is a lot more to do with timing peak cylinder pressure, more specifically when it peaks in the relation to TDC/ 18 degrees ATDC If I remember correctly, than simply the amount of fuel you inject. I don't know this engine or your pump but a dyno tune to see peak torque is all I can think of. Now that is assuming linear fuel volumes which might not be the case. This is a black art that need to be deciphered Im guessing. Still for me I run retarded....yes go ahead and throw some jokes in there, its ok....I pick up extra low end torque and a better safety margin at the expense of more peak power and better fuel economy. Once you set your timing that not simply it, other forces influence timing on a daily basis. This is where computers are helpful....what on earth did I just say.....barf......they compensate for much of that jazz continually. For us mechanically controlled guys it is a guessing game, make no mistake. A habit I've developed over the years when Im working the engine hard towing or climbing hills in the summer or stuff like that I never lug it and generally run 3-400 rpms over my usual shifting cruise range.
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It was around the 300k km mark that I put the Gturbo on and the symptoms became very clear. In hindsight it was probably actually doing it before that time. I bought the truck at 291000 km.
It ran fine except for the occasional hunt at idle when it was warmed up when fueling was stock, although EGTs seemed higher than I would have thought higher in the rpm range. When I tried to fuel it up for the GTurbo, it started to die without throttle and make rubbish power which is apparently typical; the problem is there, but in stock trim it's not seriously noticeable, except in my case with EGTs higher than would be expected.
Right. Thanks mate.
I have had my 80 for about 130k, the pump was apparently rebuilt just before I bought it. Since installing on board AFR and EGT, I have noticed I cant keep the AFR constant through the rev range and consequently as the AFR drops, the EGT also rises with the revs.
I'm thinking the advance is not keeping up to the rpms.
I have had my 80 for about 130k, the pump was apparently rebuilt just before I bought it. Since installing on board AFR and EGT, I have noticed I cant keep the AFR constant through the rev range and consequently as the AFR drops, the EGT also rises with the revs.
I'm thinking the advance is not keeping up to the rpms.
Which is very true. I've never been involved in a conversation about an engine failure where the conclusion is the engine was too retarded.
Don't stress about the AFR/EGT scenario you are seeing. I read the exact same thing. You can see from Antony's earlier post that the FT pump has a 20% increase in fuel delivery from 2400rpm engine speed to 3600rpm. Check to see the range where your AFRs and EGTs start to slide, and I think you will find this will coincide. Add to this the CT26 running out of puff around 3000rpm. I see it lose about 0.5psi from here.
I read 23:1 somewhere around 2000rpm with it sliding to 18.2 at around 3500rpm.
People told me I shouldn't have been seeing such changes in readings, and I replaced my inlet manifold gasket and bought new OEM intake ducting trying to chase a restriction or boost leak. All a waste of time and money, as the fuel delivery changes through this range.
I think I actually asked the question here as to what rpm I should tune at when chasing a figure, and Unfort the answers I got all said it didn't matter. Might be true on some engines but not these.
Also don't be sure a pump rebuild will solve the idle problem. I agree with the logic that it should, but in my case it actually caused it.
You could always get your pump bench tested before shelling out on something you don't necessarily need.
Thanks @David60series
I too have asked several places at what rpm I should be tuning the AFR to with the same answers generally. This is why I have concluded that the pump timing advance must be in its way out.
You are correct with the rpm and the boost. That's exactly how I see it in my cruiser.
@Antony why does the FT pump do this?
Is there a rational behind it?
Can it be "fixed" so this does not happen?
I would like the ability to tune to all rpm.
I have previously tuned to full throttle AFR to be on the safe side but that leaves me VERY unhappy with the lower rpm power, torque and drivavility as you may understand.
I too have asked several places at what rpm I should be tuning the AFR to with the same answers generally. This is why I have concluded that the pump timing advance must be in its way out.
You are correct with the rpm and the boost. That's exactly how I see it in my cruiser.
@Antony why does the FT pump do this?
Is there a rational behind it?
Can it be "fixed" so this does not happen?
I would like the ability to tune to all rpm.
I have previously tuned to full throttle AFR to be on the safe side but that leaves me VERY unhappy with the lower rpm power, torque and drivavility as you may understand.
I was also under the very vague and uninformed notion that tired springs would cause any counterweights/flywheel to advance earlier rather than later and as such a tired pump can advance a little too early or much on the curve and you get some black smoke.
It does this because Toyota asked for a specific characteristic and Denso provided it. You have 3 options. Bosch referred to it as torque curve and there is positive, negative and neutral and it applies to any mechanical fuel pump. Positive has fuel decrease as rpm increases, neutral stays the same and negative increases fuel as rpm increases. Its a relationship between delivery valves, cam plate, hydraulic head and fulcrum lever (in a rotary VE pump). You can build pumps into those 3 categories, I've done it for customers who have been very specific about what they are trying to achieve but it can be time consuming process as sometimes combinations don't work out as expected.
The advance is hydraulic force vs spring. As the housing/piston wears it loses hydraulic efficiency slowing the rate of advance.
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Mine used to do that in the higher RPMs as well, although I would be thinking that it's the turbo starting to choke and therefore, boost dropping a bit as opposed to the pump. With a Gturbo, I could get AFRs pretty constant with the stock pump, as it would hold boost steady to the governor if I wanted it to. With the stock turbo, mine did what you're describing.
The FT spec motor might have had an improved cam that was efficient in this range? I imagine it breathed better also.
I am probably noticing the curve more in an early combustion chamber type 1HD-T.
If you never measured AFR or even EGT you would probably never know.
I am probably noticing the curve more in an early combustion chamber type 1HD-T.
If you never measured AFR or even EGT you would probably never know.
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It would be interesting to know if the cam specs are different between the -T and -FT, does anyone have any information regarding this? The FT head would have to flow better, but I seem to remember Graeme from GTurbo saying that with a worked up manifold, a 1HD-T flowed almost as well as the -FT
I would say that the problem with boost dropping is more the exhaust side of the turbo, but I could be wrong.
Interesting you mention this as I have recently installed a EMP gauge.
I have noticed an increase in EMP With the stock turbo when the rpm rises with the same turbo boost pressure.
But the same boost pressures with with the same temperatures should result in the same AFR, regardless of the rpm. If the fuel delivery date was be same.
This is how I would like to tune.
I have noticed an increase in EMP With the stock turbo when the rpm rises with the same turbo boost pressure.
But the same boost pressures with with the same temperatures should result in the same AFR, regardless of the rpm. If the fuel delivery date was be same.
This is how I would like to tune.
I did a little more testing today.
I have tuned to 21:1 AFR @ 15spi boost on the stock CT26. I can achieve max boost at about 1850rpm. At this AFR my pre-turbo EGT will sit at around the 700C mark.
At about 2200rpm the AFR begins to drop. By about 2400rpm the AFR is at 19:1 and the EGT will be better than 800C. At this point I slightly lift my foot to drop the temps but keep accelerating, Testing max AFR every now and then. I can push to 19:1 whenever I want to within this rev range.
At about 3600rpm the AFR starts coming back and by 3800rpm I'm back at 21:1 again. It will stay here right to redline at 4200rpm.
Note - I now have a radius fab 4" snorkel and airbox. This has allowed the stock turbo to maintain this boost right up high in the rpm range where previously it would not maintain boost.
I have tuned to 21:1 AFR @ 15spi boost on the stock CT26. I can achieve max boost at about 1850rpm. At this AFR my pre-turbo EGT will sit at around the 700C mark.
At about 2200rpm the AFR begins to drop. By about 2400rpm the AFR is at 19:1 and the EGT will be better than 800C. At this point I slightly lift my foot to drop the temps but keep accelerating, Testing max AFR every now and then. I can push to 19:1 whenever I want to within this rev range.
At about 3600rpm the AFR starts coming back and by 3800rpm I'm back at 21:1 again. It will stay here right to redline at 4200rpm.
Note - I now have a radius fab 4" snorkel and airbox. This has allowed the stock turbo to maintain this boost right up high in the rpm range where previously it would not maintain boost.