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Discussion Starter · #1 ·
Hey Guys,
We are at the tail end of wrapping up putting a hellcat take out motor into my 69' Superbee. We put on the 775 injectors, 3.1 upper, headers, and 10% ATI lower. Just trying to get it dialed in now!

We had our first day on the dyno getting it tuned and dialed in. Started to get it running pretty good but it kept pulling timing on the top end. On the last pull couple pulls it started to go down hill much more and the timing was stuck fully retarded. The tuner said there is something mechanical wrong with the car but he is not sure what it is. We thought maybe it was something with the VVT.

We have checked the plugs, replaced the VVT solenoid, found oil pressure was going to my gauges and not the ECM so we corrected that, and looked at various other things. I think we made some progress as the car isn't stuck fully retarded. The engine really struggles when you first start it up. When you first fire up the car it bangs/misfires and shakes pretty bad. It does not sound very good. After it runs for a couple minutes it seems to idle much better and revs fine. The car throws no codes and we running out of ideas of where to go.

Any suggestions what could be causing it to run like this?
 

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Challenger SRT Hellcat Widebody
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The "no codes" is the interesting clue here. My first thought is a fuel system issue. What's your fuel pressure and AFR?
 

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Codes would happen for an extreme lean or rich condition. The ECM may be keeping the AFR in range but there's not enough total volume to keep the engine running. If it was on the air side, something in the boost control should throw a code. If it was spark, same thing - new code. So if there's no codes the air is there and the spark is there but the fuel isn't there in sufficient volume to keep the engine "up" but we haven't gone lean or rich in the process.

It's an educated guess is all at this point! Could be totally wrong!
 

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Discussion Starter · #5 ·
The "no codes" is the interesting clue here. My first thought is a fuel system issue. What's your fuel pressure and AFR?
Fuel pressure at start is mid 60's. The car starts idling around 1,500rpm and slowly works its way down to 900 rpm range. Stays at least high 50's. At 4,000 rpm fuel pressure is at 77 psi.
 

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That setup will make 16 psi depending on your altitude. If are are near sea level, you need bigger injectors. I run that same combo and run ID1000s (ID1050X now). No extra fuel pump needed. Did your tuner look at the duty cycle on the injectors?
 

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DRIVESRT.COM
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That setup will make 16 psi depending on your altitude. If are are near sea level, you need bigger injectors. I run that same combo and run ID1000s (ID1050X now). No extra fuel pump needed. Did your tuner look at the duty cycle on the injectors?
My thought, based upon Speedy's Garage experience with injectors, is that it needs at least ID 1050X
 

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Discussion Starter · #10 ·
That setup will make 16 psi depending on your altitude. If are are near sea level, you need bigger injectors. I run that same combo and run ID1000s (ID1050X now). No extra fuel pump needed. Did your tuner look at the duty cycle on the
That setup will make 16 psi depending on your altitude. If are are near sea level, you need bigger injectors. I run that same combo and run ID1000s (ID1050X now). No extra fuel pump needed. Did your tuner look at the duty cycle on the injectors?
I asked my tuner if it was fuel related and he didn't think so. He thinks it is something else. I have at 3,000 feet elevation here and will travel up to 5,000 feet.

I don't know what the duty cycle was at. But I know he had that parameter pulled up on the channels he was watching with HP tuners
 

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Discussion Starter · #12 ·
That setup will make 16 psi depending on your altitude. If are are near sea level, you need bigger injectors. I run that same combo and run ID1000s (ID1050X now). No extra fuel pump needed. Did your tuner look at the duty cycle on the
Sure would like some pics!
 

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I asked my tuner if it was fuel related and he didn't think so. He thinks it is something else. I have at 3,000 feet elevation here and will travel up to 5,000 feet.

I don't know what the duty cycle was at. But I know he had that parameter pulled up on the channels he was watching with HP tuners
That's a good place to start!

What transmission are you connected to? If it's a stick, that's not likely to be an issue. If it's the A8 from a Hellcat, there's small chance it's something with the conversation between the ECM and the TCM, like the TCM is asking the engine to back off for some reason...those can be tricky to diagnose...
 

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Is your Tuner experienced In Tuning Hellcats?

This sounds like the bypass blow off kicking in.

Back in 2015 When we had started the T&T + R&D of parts and Tuning with [email protected]. for Hellcats, the bypass blow off valve was very frustrating and had taken months to figure out.
There was not a single other Hellcat that could get past 9.8. Josh figured it out and my husband and I both got 9.7s
From there Josh's customers continued to go fasssster.

Tuning the Bypass blow off valve is tricky.
Other Tuners were blowing up engines. Then Josh's Tunes got passed around ( no Thank yous or acknowledgement)
And now there are many ways tune and build a Hellcat.
Also what gear is your Tuner using on the dyno?

Linda :)
 
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