Stops pulling over 3300rpm

9

98grail

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Oct 21, 2014
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HI I have the truck in sig my problem lately I found is when I'm in wot in 4th the truck will lose boost from about 50 psi to 38 40psi and wont pull as hard when I hit 3300 rpm or so. In 5th gear it pulls good to 3000 rpm or about 100mph then kind of falls on its face and doesn't smoke really at all, not like it usually does quite as smokes quite a bit but will hold 50 psi on my gauge. Do you guys think it could be a fuel pressure issue or the gsk kit is not what the previous owner says and is only a 3k kit.
 
If you are only running a 3k gsk, then that sounds like a normal defueling governor response to me. You are just pushing enough fuel and air to get the 3300 rpm. If you just put the truck in neutral and hold accelerator down how high does it free rev?

96 3500 5x018 7mm dvs 62fmw
 
Ok ill buy a 4k gsk kit then I was just wondering if fuel pressure could be a problem also. How do you like the 62mm fmw ? I have a similar setup as you but I have the 66mm old style turbo I am thinking of downsizing to that one.
 
Isn't the only difference between the 4K and 3k GSK the extra spacers? It sounded like he was saying the previous owner told him it was a 4K. Maybe pull the governor springs out and see if the 4K spacers are there?...
 
We've dyno'd a ton of trucks lately, and it's quite common for moderately tuned up 12v street trucks to lose power as they pull up beyond 3k rpm. It takes an aggressive injection pump, aggressive injector, aggressive timing, and a healthy turbo to make peak power above 3k RPM or at least hold within 10% of peak power out past 3500 rpm.

If the smoke is clearing up, then obviously there is a fueling issue, but once that is addressed, don't be surprised if it still has a noticeable power drop above 3k rpm.

Watch how much the power drops off on this 369sxe turbo test on our 95' test mule/shop truck. Keep in mind it was running mid 20* of timing, has a MAXED 640cc 5K GSK 215 pump w/Bosch peak profile cam (better refill rate with stock injection ramp), Hamilton 182/214 cam, PDD 5x018" sac 145* injectors, 165# valve springs, 7/16" pushrods, upgraded hotrod lift pump, T4 manifold etc.... basically a good hot street truck setup and as good a candidate as any to make power at 3k+ RPM. In short, around 3200 RPM it loses roughly 10% of it's peak HP that was made clear back at 2600 rpm.

[ame="http://www.youtube.com/watch?v=94j-YROdRvA"]http://www.youtube.com/watch?v=94j-YROdRvA[/ame]
 
4Ks need to be machined to work properly. Even then they don't get you to 4K in some cases. I had a set that Seth from Farrel Diesel machined and the truck would lose power at about 3,100rpm. I have a set of 5Ks now and there are 0 issues running to 4,000rpm.
 
My head was where Will's is at. Probably fuel right now, but doubtful that the charger will support peak power up to 4000rpm.

hydroshok said:
4Ks need to be machined to work properly. Even then they don't get you to 4K in some cases. I had a set that Seth from Farrel Diesel machined and the truck would lose power at about 3,100rpm. I have a set of 5Ks now and there are 0 issues running to 4,000rpm.
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I have been running Haisley 4k's in my truck for years and in friends trucks and they do 4k if adjusted correctly. They'll do more than that if tightened a little. I personally leave mine a little loose so I've got a really strong idle (important when you live in MN (-25def F in the winter) and like higher timing on a ppump).
I don't ever have to blip the throttle in order to get it to start, and it starts on about a half crank too. I absolutely love this setup for daily driving.
 
So would I be better off getting 5ks for my truck to help with this issue? Maybe ill try a lift pump upgrade will pdd new hot rod lift pump work or do I need something bigger? Thanks again for the help
 
What's the timing set at? You'll need to be in the mid 20's to make any power over 3k. Deliver valves will also be a good upgrade, stay with a mechanical pump as long as you can, unless its just a weekend driver. Keep a mechanical pump and add a separate electric lift pump off its own pickup (sump) and run it to one of the other ports in the inj pump and just run it as needed.
 
98grail said:
So would I be better off getting 5ks for my truck to help with this issue? Maybe ill try a lift pump upgrade will pdd new hot rod lift pump work or do I need something bigger? Thanks again for the help
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You should go to the autoparts store and buy a fuel pressure tester and see what happens to your fuel. If it's a fuel pressure drop, then grab that PDD lift pump (consult Will first and see if he agree's it's the right fit for your setup).
If fuel pressure is fine, or you fix it and it still does the same thing, then try tightening your gov springs. If that fixes it but kills your idle, purchase some new 5k gov springs. If after all that, you're still cleaning up your exhaust, then grab some 7mm DV's.

At that point, I'm guessing you'll have plenty of fuel, but might need to look at a bigger turbo.
 
CorneliusRox said:
Haisley 4k's .
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I should have specified Pacbrake 4Ks.

OP, I agree with everyone else, you need to verify fuel pressure first. I doubt the pump has Haisley springs, but you never know. My 5Ks are from Seth at Farrell Diesel Service. He is a sponsor and his prices are reasonable.
 
hydroshok said:
I should have specified Pacbrake 4Ks.

OP, I agree with everyone else, you need to verify fuel pressure first. I doubt the pump has Haisley springs, but you never know. My 5Ks are from Seth at Farrell Diesel Service. He is a sponsor and his prices are reasonable.
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x2 I've heard a lot of good about Seth. If I was shipping out a stock pump to him, I'd just tell him the fuel I wanted to hit. Since I, like most, built my pump one piece at a time, I just did Haisley. I've always had great experience with their stuff.
 
Forgot to mention truck has 7mm delivery valves already and timing is set at 20 degrees but ill call Will this week about that pump truck is weekend warrior with maybe a day or two I use to commute to work
 
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