Stage 1 Package - Engine Surging, Airflow Issue

[breal5825]

Has anyone in here ever added a cam to their 392? I had a Stage 1 added to my Scat Pack and, at it's core, it's a cam and ported heads. The engine is now topping out at 600hp which is SO MUCH fun to drive but... I'm now experiencing engine surge while at idle. Sometimes it's so annoying that I put the car into neutral until the traffic light turns green.

The shop that did the work has been fine tuning the car since Day 1 so it's gotten better than it was on the day I got the car back but still... the issue persists. They keep tweaking the air flow at idle but, anyone have any other suggestions?

I keep suggesting a torque converter with something like a 2,600 rpm rating. That would stop the surge power from the engine reaching the transmission and thus would quit tugging on the breaks, at least that's my thinking. It would also help me off the line and reduce 0-60 times, an added benefit. But, am I thinking along the right lines to reduce the jerking and tugging while at idle in drive?

I have attached my current tune and a couple test drives I did in both Sport and Normal modes. Any help would be greatly appreciated.
Brandon Test Drive, Sport Mode - 2019-09-04.hplBrandon Test Drive, Standard Mode - 2019-09-04.hplFull Read, 2019-08-29.hpt

[Jay@HAP]

how big is the cam?

You need a converter. There's only so much you can do with tuning.

Circle D. Don't look back.

[breal5825]

This is EXACTLY the company I discovered in my Google searches and I have been emailing Brian Burns about this situation for a few days now. The only concern I have with a higher torque converter is, when I'm at a red light and the light turns green and I lift off the break is the car going to just sit there because the torque converter holds the engine back so much or will it roll forward at like 2-3 mph like any other car? That's what I'm trying to achieve. The shaking from the motor because it's producing more power... I'm cool with that. I just want that standstill while in drive to be as much like it used to be as possible. I want a street rod, not a track or drag car. Make sense?

Side note: You don't happen to know the rating of the factory torque converter for the 8hp70 do you? I cannot find that information online to save my life.

The cam is a big cam. I mean, I'm getting 493.7 rwhp off the dyno. If you add back in the 17.5% power loss from the powertrain, you get like 598.42 hp at the crank, so I just say the engine is making 600hp. Nice round number. Here's my dyno readout if you're interested:

Brandon Bollin Dyno.PNG

[Jay@HAP]

With a high quality stall converter the car isn't going to drive much different than stock until you smash the go pedal.

The days of a 12 inch converter that is really loose and inefficient are gone.

You having a dyno sheet is even better. They can tailor the converter to your car and torque curve.

IMO, a converter is one of those things it's definitely worth spending the extra money to get a good one.

[FstdodgeKY]

I dont know the factory specs of the converter but something just under 3k stall speed would work. Your best bet is to contact whoever you want to purchase the converter from and they will need to know a few things about your setup and car to get your converter dialed in just right. As far as how the converter works you can google it and lean the science behind it, its actually quite amazing how they work. But for your question as to how it will effect daily drive ability, you shouldn't notice much a difference if you go with a good company. You may only notice a slight increase in rpm for the car to start moving but nothing major. hope this helps

[breal5825]

With a high quality stall converter the car isn't going to drive much different than stock until you smash the go pedal.

The days of a 12 inch converter that is really loose and inefficient are gone.

You having a dyno sheet is even better. They can tailor the converter to your car and torque curve.

IMO, a converter is one of those things it's definitely worth spending the extra money to get a good one.

Many, many thanks sir. I love that you mentioned Circle D too because that's exactly who I wanted to go with. I'll send them this dyno graph and let them do the rest.

[breal5825]

I dont know the factory specs of the converter but something just under 3k stall speed would work. Your best bet is to contact whoever you want to purchase the converter from and they will need to know a few things about your setup and car to get your converter dialed in just right. As far as how the converter works you can google it and lean the science behind it, its actually quite amazing how they work. But for your question as to how it will effect daily drive ability, you shouldn't notice much a difference if you go with a good company. You may only notice a slight increase in rpm for the car to start moving but nothing major. hope this helps

I actually did a lot of research on my issue and the parts of a car's powertrain to try and figure out what I needed to do to get where I wanted to be. That's what lead me to the whole torque converter idea in the first place. And yes, the science behind these things is amazing. It's a blend of fluid dynamics / chemistry and physics. I found a YouTube video with an animation of one in all three states, stall, acceleration and locked. The idea that the power from the engine to the transmission is essentially transmitted by fluid until you get to the locked phase... fascinating!

[richhurley]

Looks like it may be related to spark. Your spark minimum table needs some work, especially in the idle areas. Add actual spark to your log and then look at the min values. If you see a bunch of 3's then the minimum spark is being hit. The ECM will open the TB to get more air and fuel, to maintain the minimum timing and then close it, hence you get surging.

[breal5825]

Looks like it may be related to spark. Your spark minimum table needs some work, especially in the idle areas. Add actual spark to your log and then look at the min values. If you see a bunch of 3's then the minimum spark is being hit. The ECM will open the TB to get more air and fuel, to maintain the minimum timing and then close it, hence you get surging.

OK. I see what you're saying. So the fix would be to decrease the minimum spark so we never reach that threshold and the TB doesn't open wider. I mean, I would think I wouldn't want to set it TOO low because then, the car could stall but maybe just a few points down like 2.7 or 2.5. All depended on what the log shows. And we only want to do this for RPMs at idle speed, i.e. greater than 900 but less than 1,150 or so; my base idle is set to 925 rpms right now. Thanks. I'll give that a try.

[richhurley]

I would go even lower, I my cammed 5.7, I will see timing in the -10 when the PCM is trying to maintain the desired idle. The PCM will pull timing to adjust a high idle, so the minimum table will need to allow it get low enough to correct the idle.

[breal5825]

I would go even lower, I my cammed 5.7, I will see timing in the -10 when the PCM is trying to maintain the desired idle. The PCM will pull timing to adjust a high idle, so the minimum table will need to allow it get low enough to correct the idle.

Is there any risk of engine damage by going too low or will the only possible negative outcome be that the engine will simply stall?