compound turbo set up

Back pressure in the exhaust is only a problem in that it creates a large pumping loss which robs power. You'll never reach a limit, just lose more and more power to it.

The typical story from guys in the US with the 4BD1T's is low to mid 20 psi boost with a good intercooler is all the pump with 9.5mm elements can support. Someone (maybe Randy) had his pump measured at ~140cc/1000 shots.

And I'm happy to say all these numbers check out. There is no BS involved.

If you can get your setup running at optimum for power then you can get a clean 590Nm at 3,200rpm. This is close to 200kw at the flywheel.

If you can get your setup running at optimum efficiency for max torque then you'll hit around 630Nm at 1800rpm. This is around 120kw at the flywheel at 1800rpm.

4" seems like a minimum requirement for those 'big' Cummins 4 and 6 BT engines. I'd say you will be approaching this requirement judging by what Dougal says regarding the pump mods and required airflow....

Air in, Air out....:twisted:

Good Stuff J, looking impressive.

The other J (C)

Ok
Pretty much certain my pump needs attention. The scenario is

Fuel screw basically all the way out
Minimal smoke from midrange up

In top gear say 100 to 110 which is near the limit with our tyres and gearing. The engine is very erratic on throttle response. If you accelerate or decelerate slowly it's erratic like you are crimping a fuel line.

Now this motor has always had this problem, only to a much smaller degree, the compound set up has magnified it.

Open to all pump suggestions before it comes off for a trip to the test bench.

Justin

No smoke is the way it should be. So that's not a problem you should be fixing. That just means you have enough air to burn all the fuel cleanly.

The erratic behaviour, certainly look into that.

How is the power and torque feeling?

Quote:

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Originally Posted by DRanged

Ok
Pretty much certain my pump needs attention. The scenario is

Fuel screw basically all the way out
Minimal smoke from midrange up

In top gear say 100 to 110 which is near the limit with our tyres and gearing. The engine is very erratic on throttle response. If you accelerate or decelerate slowly it's erratic like you are crimping a fuel line.

Now this motor has always had this problem, only to a much smaller degree, the compound set up has magnified it.

Open to all pump suggestions before it comes off for a trip to the test bench.

Justin

---

Justin, I have a similar fault with mine (NA pump) and it is now sort of fixed itself, hasn't done it for ages. The diesel pump tech I explained the symptoms to THINKS it is indicative of a sticking fuel governor, but obviously his advice was "Maaaaate, bring 'er in we'll take a look on the bench...'" which I read as "you'll need a pump overhaul..." :eek:

JC

Quote:

---

Originally Posted by Dougal

No smoke is the way it should be. So that's not a problem you should be fixing. That just means you have enough air to burn all the fuel cleanly.

The erratic behaviour, certainly look into that.

How is the power and torque feeling?

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Power and torque is very smooth and linear to say 3/4 throttle . From then on say 18-24 psi it struggles and will only respond properly if you put the pedal to the floor. I am leaning towards a pump check I think. Over the weekend I will **** off my neighbors in the valley and run it just with the dump pipe for comparison.

Justin

Quote:

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Originally Posted by justinc

Justin, I have a similar fault with mine (NA pump) and it is now sort of fixed itself, hasn't done it for ages. The diesel pump tech I explained the symptoms to THINKS it is indicative of a sticking fuel governor, but obviously his advice was "Maaaaate, bring 'er in we'll take a look on the bench...'" which I read as "you'll need a pump overhaul..." :eek:

JC

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Jc
Mine is also an NA pump. I think it could be the Govenor now you mention it. Might pay just to get it on the bench to see. The local pump guy is a genuine bloke so all should be good.

JL

Exhaust should be pretty quiet with two turbines in it.

Was idle effected ? Maybe this irrational behavior is due to all the different air fuel ratios as there is now 2 of everything at play and getting the 2 working/crossing over in the optimal efficiency range may feel like a irregular power delivery...I'd get them to look at the torque cam profile however as Justin said "most" injection specialists do actually mean rebuild when they say test... If the fuel screw is all the way as in cam sitting on its rest try winding it in just a tad see if anything changes..

Idle through to 3/4 + throttle is very good. Fantastic turbine noise at idle and mid range after gear change I might add. I think the inevitable has finally caught up with me re the pump.

Dougal, yep I hope it is quiet, but the dump pipe is only about 900mm long

J