Highest Microseconds to run.

[catman3126]

I have tuned a lot of 6.7's and recently I tuned a 6.7 that had an edge with hot unlock settings on it, and when I was driving it with the edge on it I could tell right away that the edge was going to have a lot more power than a 3000Us tune. and one truck that came in for efi live that had a tune in it and the guy didn't know anything about it so when I downloaded it I saw that the US was at 4800 in the bottom right hand corner. And let me start by saying I would never want to tune one up that far due to the way it ran and it smoked so bad. so how far can these be tuned up? I know that the rule of thumb is that at 3K Us you need to start thinking about bigger nozzles but at 3K they run good but not like that one that had 4800Us obviously. the customer that had the edge with hot unlock wants that amount of power back. He towed on that setting and everything. Can the cummins take a higher pulse width then a duramax? thanks

[ATPCummins]

A customer sent me a data log a while back and he attached the wrong log by accident. The log was of his old "box" tuner and I saw an unbelievable amount of duration as well. The truck ended up making an additional 31hp on about 900 less microseconds. You are already about as far as I like to go with duration, and I don't go that far with a stock turbo and stock head bolts.

[catman3126]

This truck is studded and he keeps wanting it turned up more. But is also on a stock turbo. what do you do in this situation? turn them guy down and say you won't turn it up anymore? I also wondered what would happen if I did a all stock single delete tune for the guy and hooked his edge juice back up so he is happy with the power again. he says he likes the efi live CSP5 setup but wants the edge amount of power. Not sure what to do here.

[Mitco39]

Fuel is just one part of making power. Its really (safe) cylinder pressure is what your after. The right combination of fuel to timing will yield the biggest push down on the piston. Adding fuel much past TDC will only increase temperatures across the board. More fuel needs more burn time and thus more timing to properly control the cylinder pressures that that peak pressure occurs at a crank angle that will generate the most amount of torque for fuel burned.

In cylinder pressure transducers or at the very least a dyno would be the proper way to deal with a truck like this. I to have come across customers like this and all you can do is be 100% clear that you are starting to push the engine into a territory that may begin affecting its life.

[catman3126]

That's exactly what I told him yesterday and his response was "If it blows it blows" I'm running 28 deg of timing at 3200 rpm. I'm really surprised aboput how little he cares about his motor. yeah so do you turn it up or tell him no? I'd rather not have a rig I tuned take a shit lol and them have him bad mouth me. I don't think he would but you never know.

[catman3126]

Yes I agree and know that a longer pulse width creates a situation where the fuel is not being sprayed in the chamber and is spraying the top of the piston.

[catman3126]

I should post that tune that had 4800Us in it. bad thing was that it was a delete tune and the person who traded it off put the DPF and stock exhaust back on. when I drove it he said step on it and watch how much it smokes. it blacked out the hiway even through the DPF. when I took it off it had 1'8 thick flakes of carbon falling out of the inlet.

[Mitco39]

I know the type. I have always just made it 100% clear but I know what you mean. I had a situation where one kid wanted a similar type of setup on a Dmax. Made him aware of it all, he chose to run it on that tune with no EGT gauge or anything and it went pop. I dont know what some people expect. Thankfully they are far and few in between.

[catman3126]

How much you turn that one up? the highest I have ran in my LLY is 3100Us, been there for 40K but I don't race or sled pull just the WOT run up to 120-130 and the egt's get up there ways but still running stock head bolts and gaskets at 104K

[ATPCummins]

When a customer is determined to push his truck farther that what I feel comfortable with I sometimes send him an estimate for what it will cost if it fails, and put in the notes that pushing the truck that far is not advised. Helps cover my butt and he knows what he is in for.