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Discussion Starter #1
I recently had a vortech sc installed and a dyno tune on an 08 SRT challenger at a local performance shop. The vehicle now has random missfires (code PO300) when I put my foot in it. Car runs strong however, misfires at high rpm.

How common is this, what factors could contribute?

I run 93 octane
Plugs were not changed during install
Re-tune by someone with more (hemi) experience?


Thanks for any constructive feed back.

Scott
 

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The plugs should be replaced with a set that are at least one range cooler than stock. Also, your tune probably needs to be adjusted.
 

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One step colder will be plenty on low boost,Other wise you may foul the plugs.. That being said,grab a set of NGK 2315s and gap to 035 and those codes will clear right up.

If you dont have the coin for the plugs you could get away with re gapping your stock plugs as that what vortech suggests but that wouldnt be the best thing IMO.. Best of luck..
 

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Plugs must be gapped, as stated try that and seemif that helps, I would also suggest having someone with hemi tuning experience look at the tune if it was tuned by a shop with little FI hemi experience
 

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Gap the plugs down. I'm running stock plugs in mine and at 12-13psi of boost mine are gapped to .030. Yours won't need to be gapped that tight for 6lbs of stock Vortech boost, and I'd say the .035 suggested above isn't bad. One step cooler can't hurt, but like I said my engine builder used my stock plugs in mine.

Take a good look at the plugs when you're regappinng them. Look at them under good light with a magnifying glass. Make sure there's no metal looking flecks on them.

With as sensitive as the stock engines seem to be I'd never take a misfire code in one of these lightly.

What's your air fuel ratios? How much timing does the tune give the motor?
 

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Discussion Starter #8
Gap the plugs down. I'm running stock plugs in mine and at 12-13psi of boost mine are gapped to .030. Yours won't need to be gapped that tight for 6lbs of stock Vortech boost, and I'd say the .035 suggested above isn't bad. One step cooler can't hurt, but like I said my engine builder used my stock plugs in mine.

Take a good look at the plugs when you're regappinng them. Look at them under good light with a magnifying glass. Make sure there's no metal looking flecks on them.

With as sensitive as the stock engines seem to be I'd never take a misfire code in one of these lightly.

What's your air fuel ratios? How much timing does the tune give the motor?
AFR; min 12.0, max 13.5, avg 12.4
timing advance; max22, avg 13

Thanks guys for the feed back
Scott
 

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Speedy posted my question. What's the AFR... I'd look to get it down in the low to mid 11's when you're at WOT. I'm thinking you're a bit lean, especially on a stock block.

HemiSam
 

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AFR; min 12.0, max 13.5, avg 12.4
timing advance; max22, avg 13

Thanks guys for the feed back
Scott
That's too lean on a stock motor. I'd want it 11.2 - 11.3. Definitely no higher than 11.5 for sure.

I'm not sure how you're getting the readings, but on the timing, what I wanna know is what is it with the pedal to the metal. The timing should stabilize and be at a set value give or take a tick.

With where you're at now, I'd not drive the car in to boost. These motors will pop in a heart beat without a good tune.

Where are you located....we might know a good tuner in the area that can help.
 

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Yes...too lean...check the plugs for gap as well, but I would look at having that tune looked at before hitting it hard. FYI, the Vortech systems come with a VERY safe canned tune, do you know if you purchased a complete system or a tuner kit? If it is a system that comes with a Vortech canned tune you should be able to load that, it will be much safer than what you are on now, you can always get that tweaked by a good hemi tuner.
 

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Speedy,
Numbers listed (AFR & timing) are from dyno tune sheet.
Located in north GA.
Thanks.
Gotcha. Well, it needs adjusting. Don't get in to boost until it is, or load the Vortech canned tune that came with the supercharger like SRT8U said. The tune you have now could kill that motor.
 

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Discussion Starter #14
Vortech SC...random missfire.

Solution to the problem......HHP, Charleston SC.
Thanks Jeff & Jamie.
The thing runs like a champ.

Scott
 

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thats good to hear what was the problem?
 

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Wow, yeah that was lean, holy cow man! Glad you asked questions before it popped a piston.

What are the timing and air fuel ratio parameters now?


Why no methanol injection?
 

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My Vortech tune was Lean also. It would get the misfire code. I thought canned tune it would be fat, and it wasnt in mine. Something about the injectors not being scaled right. Dyno Steve at RDP hooked me up from my stock NA tune and built my SC tune. I gauge and log A/f its 11.5 at wot it takes a bit fot it to get there.
Gap in my plugs Vortech had me set at was 28th to 30th one step colder.
FT
 
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