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Got a tune on my 383 tpi. Falls flat around 4k..tuner at dyno Shop in Santee ca said it most likely is air flow issue. They did multiple hits with different timing and advance and nothing solved it.
any ideas?? Or is this a common tpi style intake issue.
I have no idea. Lol. It's making me mad. Had a couple hits at CCC motorsports in lakeside a few months ago..graph was wayyy smoother. Not sure what the deal is
Ignition issue? Was it a problem with the dyno signal pickup or something?
Valve float usually acts like a wavy erratic line and not a big drop off like that with it continuing to climb again.
Could this be an issue with the stock throttle body?
or tpi intake altogether?
You already said you made a previous hit that was way smoother, so how could it be the stock throttle body or TPI intake altogether? Anyways, looking at the graph it looks like you slapped a TPI system w/siamesed runners onto a modded 383 w/stock L98 bin. Meaning you are tuned up until 4000-RPM, then the increased airflow comes in, airflow in which you are not tuned for, and power drops eventually catching itself. You said you made multiple timing changes, but where? Did you at least tune the SA Main Table, or were you referring to just Base/Idle SA? What was the air/fuel throughout the pull? Can we see a copy of the bin? Information like this will immediately pinpoint what is wrong.
I'm also running a 383 with ported TPI, similar cam, but more lift, and I'm also running Holley HP EFI. I'm pulling strong to about 5500. haven't dyno'd yet since the self tuning went well, and I've just start dabbling into ME tweaking the tune a bit to find power. I was hoping that a dyno tune would be my last step. ...but I can tell you I don't have any power drop like what you've posted. Heck I don't think I've ever seen a 200 RPM drop like that!
What is your datalog showing you? What about fuel pump/pressure? New pump? You keeping pressure all the way through the run? What are your fuel compensation table values right before you drop off that cliff?
I don't have NEAR the engine building experience some of these guys do, but I just cranked my engine this past December, and I'm also using the same engine management/Holley HP system. V E R Y Familiar with the ins and outs at this point!!!!!!!!!!!!! I'm very happy to help!
You already said you made a previous hit that was way smoother, so how could it be the stock throttle body or TPI intake altogether? Anyways, looking at the graph it looks like you slapped a TPI system w/siamesed runners onto a modded 383 w/stock L98 bin. Meaning you are tuned up until 4000-RPM, then the increased airflow comes in, airflow in which you are not tuned for, and power drops eventually catching itself. You said you made multiple timing changes, but where? Did you at least tune the SA Main Table, or were you referring to just Base/Idle SA? What was the air/fuel throughout the pull? Can we see a copy of the bin? Information like this will immediately pinpoint what is wrong.
I wasn't there for most of the tuning. And I know very little about it. Getting a laptop this month so I can try and learn. The bin is the Spark Advance table?
Ignition issue? Was it a problem with the dyno signal pickup or something?
Valve float usually acts like a wavy erratic line and not a big drop off like that with it continuing to climb again.
trans is supposed to have transgo hydraulic lockup. Not sure honestly.
Reason i ask is the stock bin has a setting to lock converter at wot. Somewhere around 88 mph. Usually drops the rpms/slows the pull down abit at that instance, but power usually goes up as there is no loss of power in the converter slip with the converter locked
Had a couple hits at CCC motorsports in lakeside a few months ago..graph was wayyy smoother.
Originally Posted by kevwalt22
Got a tune on my 383 tpi. Falls flat around 4k..tuner at dyno Shop in Santee ca said it most likely is air flow issue. They did multiple hits with different timing and advance and nothing solved it.
Originally Posted by kevwalt22
I wasn't there for most of the tuning. And I know very little about it.
This is what I think the problem is. Not taking anything away from that dyno shop that did the tuning, but I am almost convinced they missed something in the tune, or at the very least inadvertently made a change that they cannot find. It ran fine, you got a tune, now it falls flat on its' face. Bad tune, tuner can't find what's wrong. Get a copy of their tune asap.
Reason i ask is the stock bin has a setting to lock converter at wot. Somewhere around 88 mph. Usually drops the rpms/slows the pull down abit at that instance, but power usually goes up as there is no loss of power in the converter slip with the converter locked
No I don't have converter harness even installed for computer to control lockup so I don't think it's that.
This is what I think the problem is. Not taking anything away from that dyno shop that did the tuning, but I am almost convinced they missed something in the tune, or at the very least inadvertently made a change that they cannot find. It ran fine, you got a tune, now it falls flat on its' face. Bad tune, tuner can't find what's wrong. Get a copy of their tune asap.
let me rephrase. Tune at CCC motorsport was bad. Misfires on half and quick full throttle, very hard starts, and high erratic idle. They said misfires could be stock fuel pump because the fuel pressure was dropping slightly. I replaced with a 255lph. Still Misfires. Fast forward to now. Took it to DynoShop in Santee. No Misfires, good idle, altogether smoother running engine, but power drop issue
...almost everything we're discussing can be diagnosed/crossed off the list by having access to a laptop hooked up to the ECU and data logging. Are you paying this shop to pull a dyno run, or to TUNE the car???? ....if they're tuning, I'm surprised they can't SEE what's happening on their datalog. ....and if the engine didn't fall on it's face BEFORE you brought it to them, and they smoothed out the idle etc. etc, but now it's falling on it's face.....it's gotta be their tune!
...almost everything we're discussing can be diagnosed/crossed off the list by having access to a laptop hooked up to the ECU and data logging. Are you paying this shop to pull a dyno run, or to TUNE the car???? ....if they're tuning, I'm surprised they can't SEE what's happening on their datalog. ....and if the engine didn't fall on it's face BEFORE you brought it to them, and they smoothed out the idle etc. etc, but now it's falling on it's face.....it's gotta be their tune!
it never ran good enough for me to tell after the first tune from CCC motorsports. The graph on the printout they gave me had a nice looking, smooth curve. Must have been bs. I'm buying a laptop this week so I can learn and look at everything that was said here.
I paid the shop for the tune. They said "they can see everything when tuning" and couldn't figure it out.
I think getting that laptop is key. Nothing like being able to invest your own time into it. While I'm no tuning pro, I'm very familiar with the Holley HP, and I can help you out a good bit getting things going. The amount I've learned just in the last 4 months of having mine running is amazing.
Just to be clear, I'm not discounting anyone elses knowledge or opinion as to what your problem is. MY point is that once YOU are familiar with the system and have all the data on your laptop in real time, I think YOU can figure out a lot of what's going on, rather than simply pay someone else, and still not have your problem fixed. Then when you DO come onto this site, you can better answer some the questions these guys have.
In the meantime, get the Holley software loaded on your PC. Honestly if I were you, I'd start over completely. Obviously you can't tune from your PC, but you can slowly go through it step by step and set up basic tune parameters for your engine. Fuel injectors, offsets, displacement, ignition, and a host of other little things. Plus you can learn all the different tabs, screens, tools, etc. etc.
...then....once you DO get it loaded on your laptop and ultimately into the car, you're already familiar with the software. The system does a decent job of self tuning, but you gotta have that base calibration set up properly.
The self tuning won't tune as well as a professional tuner could, but it should do well enough to determine if you have mechanical issues or tune issues. You can get that worked out on your time, with no extra costs (hopefully). Then you can do as much or as little performance tuning on your own, and then of course you can STILL always take it to a professional shop. That's been my plan, and why I chose the Holley. Thus far it's working well for me.
03-30-2017, 02:07 PM
