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Discussion Starter #21
My dyno shop got back to me said it's an Injector problem I bought the fuel injector clinic 1000s since iam only putting 676 whp. Said was a bit tricky since car is not using full potential of Injector. And when cool will be a rough a bit till warmed up. If that's the case iam gonna have to live with it and really cant say its any fun to drive this car when its 50 or below feels like iam on ice it wont hook even if put the throttle down half way. What do you guys think dyno shop right or keep digging?
 

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My dyno shop got back to me said it's an Injector problem I bought the fuel injector clinic 1000s since iam only putting 676 whp. Said was a bit tricky since car is not using full potential of Injector. And when cool will be a rough a bit till warmed up. If that's the case iam gonna have to live with it and really cant say its any fun to drive this car when its 50 or below feels like iam on ice it wont hook even if put the throttle down half way. What do you guys think dyno shop right or keep digging?
Like you I am also in Wi... I'm running ID 1000's on my Procharged Scat with HC short block and don't have any cold start issues. who tuned it ?
 

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My dyno shop got back to me said it's an Injector problem I bought the fuel injector clinic 1000s since iam only putting 676 whp. Said was a bit tricky since car is not using full potential of Injector. And when cool will be a rough a bit till warmed up. If that's the case iam gonna have to live with it and really cant say its any fun to drive this car when its 50 or below feels like iam on ice it wont hook even if put the throttle down half way. What do you guys think dyno shop right or keep digging?
Well, I guess it comes down to how much you trust the dyno shop.

You should have asked for a more indepth explanation of what was meant.

All I can think of is it is possible I suppose a high performance injector may not take light duty that well. But the injector pulse width cold I think would have to be longer than the pulse width with the engine up to temperature.

Thus if the injector can supply a hot idle amount of fuel without any issues it should be able to supply a cold idle amount of fuel without any issues.

Even if during cold idle the injector was called up to inject two times, once at the start of the power stroke and again during the exhaust stroke. This 2nd pulse to supply a bit of raw fuel to the exhaust where it will be burned to heat up the converters.

If an injector can't handle two pulses of fuel at cold idle speed how could it handle power stroke pulses at max engine speed where the pulses would be separated by just (est.) a few hundred microseconds?

Unless I'm missing something and that is always a possibility blaming the injectors seems kind of fishy.

Howver, it just occurred to me: Maybe the injector spray pattern isn't optimum for low engine speed operation? A high performance injector may be designed to deliver a spray of heavier/larger droplets of fuel rather than a fine spray due to the amount of fuel the engine requires and the brief window of time the injector has to get the fuel in the cylinder.

At higher operating RPMs the air breaks the droplets up and the heat of the combustion gases exposed surfaces heats the incoming charge up which helps vaporize the fuel droplets. But at low speed the droplets are still rather intact and with cold combustion chamber surfaces cold combustion efficiency suffers.

As a band aid, maybe a slightly higher cold idle engine speed could help?
 

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Discussion Starter #25
Thanks for the reply rockstar , I dont think that the shop would pull my chain car and truck have had multiple tunes they all been fine except this one now on a cold day. I was there watching him dyno this last time everything looked good no knock,no detonation air fuel at 11.50 nothing strange
 

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Rockster I don't know where you are getting the idea the injectors double pulse? The injectors do not double pulse (nor do spark plugs fire multiple times) on these engines...single pulse per complete cycle. Hard to tell what is going on at cold start up if you are not monitoring AFR during crank and startup. The OEM O2 sensors only work after they have had time to warm up which can take +30 secs. It also depends on how the shop tuned the engine...NN is on (PCM algorithms are calling the shots when CL is reached), NN is off (PCM uses VE tables and system is forced to run in OL)....ect.

For startup issues tweaking the injector pulse widths can help achieve a "clean" startup.
979919


Otherwise making tweaks to cold engine enrichment can help but again, all depends on how the tune is set up. I would work with the shop to have them make the cold startup tweaks as they most likely tuned the car in warmer temps.
979920
 

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Discussion Starter #28
Jesse is dam good I go to him for all my maps he fixes problems that other shops give up on. Car was tuned 85 degrees 50 percent humidity. Ay least its somewhat i feel figured out between your guys help the torpedo heater tests ( car start up was great) Nd from what dyno shop said. I will probably swing up there glad iam close. But really I can deal with it as long as there is no engine damage going on. Like I said only 50 degrees and under it does it.
 

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I wasn't suggesting your tuner was missing something, instead the car was tuned when ambient was much warmer and might need tweaking for colder weather. For example, if I adjust my fuel trims during summer weather, they tend to be an the lean side in colder weather.
 

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Discussion Starter #30
I know tatum that first part was directed to white rt. iam glad you guys hit this thread up you guys seem to be very knowledgeable on fuel trims. I swear I've been a bit of a car hypochondriac after my buddy and I tore this thing down iam like that guy now from that carmax commercial talking to the car with a stethoscope in hand
 

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Challytatum has a good point ....maybe something was overlooked or not considered . probably just needs a tweak.. . if you haven't spoke with Jesse directly..you should..he will want to fix it..
 

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Discussion Starter #32
Yeah iam gonna call cody get the car in. So they can bump up the idle I doubt it needs to be put back on the dyno for this
 

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My info is that at least in some engines during a cold idle before the converters are hot the engine controller injects fuel at the power stroke of course, but also during the exhaust stroke a smaller bit of fuel is injected to provide extra fuel to burn in the exhaust to more quickly heat up the converters. The 2nd pulse of fuel is not sparked but is ignited by the hot exhaust gases.

(I could hear this from my Turbo: I could hear small backfires from the exhaust system -- not at the exhaust tips -- from this extra fuel burning.)

If the Dodge engines don't do this then of course never mind.
 

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Yeah but we are focused on a Hemi specific problem I would try to keep the info specific to Hemis and not sight other examples of how fueling is handled on other brand motors this can lead to misdiagnosis of the problem.
 

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I'd lean toward issues with tuning.

OEMs go through all sorts of testing / tuning for both emissions and driveability for cold and hot operation.

this is where they'll go to the hottest and coldest places around the US as well as high altitude areas as well. The goal is the vehicle operates in all temperatures and conditions properly.

there's cold start / run timing profiles (both for cam timing and ignition timing) as well as getting the engine from open loop (cold start up) to closed loop (monitored) operation to in as short a time as possible for cleaner emissions vs. the baseline values used for open loop operation

good tuning involves not just aiming for the highest dyno numbers possible at the top end, but to have it actually run across the rpm band smoothly
 
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