No torque at the high end August 10, 2015 11:13AM
Trying to help a friend so here what I know.

Its a 531cube JD with a P-pump currently running set for about 725-750cc, 3000rpm running in a speed limit class. The tractor comes out of the hole strong and has no problem getting down the track but, once the box gets ahead or the pan drops fully it falls right off. It goes right under the turbo instead powering out, spinning out. What I know is they have timing set about 35 degrees, Im told factory is 30? Stock pistons, stock cam, head fully ported/polished. What I dont know is exactly what they are running for a turbo but they have now experiamented with a smaller exhaust housing machined to fit a big wheel and it hasn't really made a difference. it also runs an ice water cooler on the turbo intake.

Right now theres a lot of guessing going on about exactly what to do next. I wonder if they should actually take some fuel away? My theory is when they are running at the speed limit the pump isnt up on the govenor and engine isn't loaded heavy demanding fuel and when the load hits the fuel dump full load might be putting the fire out? I also think they should take away some advance. Any input is appreciated.

Just trying to help with a few runs left this season Id like to see them get it figured out before they go into winter scratching heads wondering WTF?

THX!

**Posted in the wrong place first time, sorry
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Re: No torque at the high end August 10, 2015 02:05PM
take away at least 125 cc of fuel. with head ported you will need a cam. head flow is to much for stock cam. will not pull at all like that. will fall flat on it face when load hits. probably very sluggish now even from the get go.
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Re: No torque at the high end August 11, 2015 05:34AM
I agree, take away some of the fuel and I would put the timing down closer to stock maybe try somewhere around 28 to 32 degrees. I don't know if you have a pyrometer installed but try to get the egts up to near 1550-1650 degrees. Id be willing to bet you have a lot of black smoke and little to no visible fire out the stack going down the track. If that is true, then cut the fuel back and watch it come to life.
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Re: No torque at the high end August 11, 2015 05:47AM
Thanks for the suggestions, confirms my suspicions and also brings to light the stock cam limits with the high flow head. Next move is timing down to 28-32 range, take fuel away, at least a full turn to start. See what the pyro does and use 1600 for the target. next pull is two weeks out.
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Re: No torque at the high end August 11, 2015 04:32PM
1600 degrees is WAY too hot. And you DONT want fire coming out of the stack. Unless you like working on it all the time.
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Re: No torque at the high end August 12, 2015 12:22AM
At 1600 degrees your engine should last forever.I run 1800 to 1900 pistons look like new after a year.Agree on cutting fuel back.Seen it help many times.
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Re: No torque at the high end August 12, 2015 12:42AM
if you were towing a trailer up a mountain 1600 would be bad. however for a short burst like a pulling track 1600 is extremely normal and I know a lot of people who run hotter than that with no problems.
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Re: No torque at the high end August 12, 2015 06:00AM
1600 with stock pistons is too much. If you get Riverside pistons, they will take it, but stock pistons will not. Prove it to yourself, run it at 1600+ but buy another set of pistons so you will have them on hand--sleeves also, you will wreck them to.
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Re: No torque at the high end August 12, 2015 06:29AM
Where do you want that temp read before or after turbo? We take after turbo and are running 1300-1500. How much temp difference is there from before to after?
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Re: No torque at the high end August 12, 2015 01:59PM
May sound stupid but I would check fuel pressure . I had the same problem
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Re: No torque at the high end August 13, 2015 10:35AM
What was the deal with low fuel pressure? I'm Curious if that may be part of our problem.
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Re: No torque at the high end August 23, 2015 06:04AM
1600 way way way to hot way to hot lmao!!!
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Re: No torque at the high end August 13, 2015 12:03AM
The temperature should be taken before the turbo. The temperature will be 300 to 400 degrees lower after the turbo. (that is what drives the turbo) It takes energy to drive the turbo, if there was no difference in the temperature before/after, the turbo would do nothing, no energy expended, no work done. People that think you need 1600 to 1900 degrees to make power should talk to superstock guys--they commonly have 1300 degree exhaust temp and make 3000+ horsepower. Remember this: 1200 degrees is cherry red! To make more than stock horsepower, your head, cam, turbo, pump, and injectors all need to be right. A happy motor will make power, an unhappy motor will not. You may say "I have the best head money can buy", but if the rest is not right, it won't make power. It all has to be right.
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Re: No torque at the high end August 13, 2015 05:37AM
Makes no sense to talk about EGT unless you specify how far from piston,- head or cylinder chamber.
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Re: No torque at the high end August 22, 2015 02:20PM
to all: FOLLOW UP!

So timing got reset to 30, fuel turned down to what we estimate around 600-625cc (Based upon the notes from the pump builder distance of fuel screw measurement to cover).

2 Runs in now, Pyro reads 1450 *Before turbo at mounting flange under it and runs much better and responsive. Not saying there still isnt more to be had but with stock cam and with limited turbo choices and with season nearing the end everyone has a better feeling about where things are now.

Basically they learned to you really can put the fire out with too much fuel, they just needed to learn it the hard way.

Thanks to those who chimed in!
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