24v Power Issue: Help Solve

coon smile

coon smile

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Oct 25, 2007
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Long story, but bare with me:

Traded a set of 6x13's for a set of 7x14's. Picked up noticable power with the 7x14's. EGTs were up to around 1200-1250 WOT, and boost was up 5psi to just above 80psi total. One problem though - one of the injectors has a bad knock (checked this by craking the injection line at the head, and the knock followed the injector). Sent the injectors in to have them checked out, and a couple did not pop well, while the one that was knocking had the injector body replaced with a new one. I put the 7x14s back in today, after being serviced, and they still had a bad knock, along with black smoke at idle. I put a set of my buddy's Mach 7's in the truck that came out of Bowersock's old pulling truck (had them all popped to 300 bar before I installed them). I installed them before I headed to the track tonight, and the knock went away. So now I know the 7x14's have an issue, but they run great when your WOT. With the Mach 7's, I can only hit 60psi after the truck locks into OD, and that is with only 20psi out of the primary. Clearly the power is down. I checked the wire tap on the stealth cover, and the ground is good. On my way to the track, I was on the highway, and I floored it to compare them to the 7x14's. The boost climbed fast, and then it almost felt like it sputtered for a split second but continued pulling smoothly to 60psi WOT.

Bottom line is the truck is down serious power after only changing from a 7x14 to a Mach 7. I don't see it being injector related, and it feels like the drag comp is not fueling at all. My truck will make a little over 60psi without any electronic fueling, so I am thinking it is related to the drag comp. It's not just the drag comp box itself, because it runs the exact same with my other friends drag comp. Maybe something in the harness of the drag comp?

Any Ideas?
 
Doesn't that set of injectors have 12v compression springs?
 
Smokem said:
Doesn't that set of injectors have 12v compression springs?
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No clue. I was told they were not his "conversion" injector, if that's what you mean, and that they were just the same Mach 7's that Don sells for the 24v.
 
I didn't realize I posted this in the Drag Racing section. Will a mod please move this thread? Thanks.
 
I wonder if your comp is getting a good MAP signal? I know when it rains, my comp sometimes just will not fuel and I think its due to a bad MAP connection, just havent had the time to track it down.

I wonder how much PSI the factory MAP sensor is good for? I suppose its possible you could have blown it at 80 lbs.
 
bosshogg said:
I wonder if your comp is getting a good MAP signal? I know when it rains, my comp sometimes just will not fuel and I think its due to a bad MAP connection, just havent had the time to track it down.

I wonder how much PSI the factory MAP sensor is good for? I suppose its possible you could have blown it at 80 lbs.
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The map sensor is about a year old, and I checked that connection at the track last night. It looked good. All of the connections look good with the comp, but I am not sure.
 
have you considered swapping the 7x.14's back in and running it @ WOT kyle?

-Seems like that would at least narrow your problem...

a) Runs the exact same hitting only 60 psi -> Electronic related

b) Injectors

Idk.... just my .02
 
bbtank45 said:
have you considered swapping the 7x.14's back in and running it @ WOT kyle?

-Seems like that would at least narrow your problem...

a) Runs the exact same hitting only 60 psi -> Electronic related

b) Injectors

Idk.... just my .02
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Aren't you supposed to be out at Stang's farm?

I thought about swapping the 7x14's back in today, but I have been swapping injectors in and out of the truck the past two weeks. I needed a break and a day off from working on my truck. Plus the fact that the one injector is knocking and smoking black at idle kinda tells me that I shouldn't be running them in my truck.
 
coon smile said:
Aren't you supposed to be out at Stang's farm?

I thought about swapping the 7x14's back in today, but I have been swapping injectors in and out of the truck the past two weeks. I needed a break and a day off from working on my truck. Plus the fact that the one injector is knocking and smoking black at idle kinda tells me that I shouldn't be running them in my truck.
Click to expand...

I ended up going to John B.'s house for his bonfire.... havent seen him since his 21st and his brother isnt doing so well
 
Kyle, when i was following you to the track i remember seeing The smoke sputter from your stack when you were wide open throttle.... I would take the stealth cover off the pump to make sure it is getting tapped
 
LAmiller said:
Kyle, when i was following you to the track i remember seeing The smoke sputter from your stack when you were wide open throttle.... I would take the stealth cover off the pump to make sure it is getting tapped
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Yeah, when I felt that slight hesitation before it started pulling again, I noticed a break in the cloud of smoke out of the stack.

I would have just figured that since we were seeing 12.6v at that screw on the stealth cover and that the connection was good, the tap should be fine.
 
*Update*

I switched the Mach 7's out for Glenn's 6x16's, and the truck has never pulled so hard. The boost and power I lost, after switching from the 7x14 to the Mach 7, is back. I am guessing something is not quite right with those Mach's, or maybe they just don't fuel as much.

I am going to back this up with a trip to the track on Friday and a dyno run on Saturday, if everything goes as planned.
 
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