When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Using the truck coils, the plugs are gapped at 25, the highest gas off the street I can get is 91 and fuel pressure is 58 when the vacuum is off the fpr. I have 2 walbro 255 in tank. Fast fuel rails -8 feed and using the stock feel as a return. Meth hasn't really been tuned in but is set to come on at 10psi and full at 15psi.
You have multiple problems. Something mechanical may be going on (probably), but a prerequisite for being a good tuner is knowing how to diagnose mechanical issues. This means your tuner is incompetent on top of whatever other issues you have.
This isn't the 80s anymore. Common turbos spin much faster with boost than without.
Seriously? I've personally seen turbos eat themselves, new BWs and Precisions because a charge pipe came off and the owner didn't realize it. This is nothing new and it has nothing to do with not being the 80s.
Your graph looks like valve float, also having the exhaust change it's sound as a tell tale as well as it not accelerating as fast through the RPM range up top as it did in the lower RPMs. I don't care what the tuning school says it's not always true.
As far as I read, I didn't see you say how much actual time he spent tuning it. Lots of people said the tune was a mess. I didn't even look, but I do know some tuners (mostly bad ones) will tune wot first. Most of them stop right away if it's not going well, tell you there is a problem and demand payment. Tell you to come back when it's fixed.
Imo, it sounds like there is some issue going on, but I would probably find a different tuner as well. If he doesn't spend the time to get the remainder of the tune correct in this type of issue, he is a shitty tuner. JMHO
Your graph looks like valve float, also having the exhaust change it's sound as a tell tale as well as it not accelerating as fast through the RPM range up top as it did in the lower RPMs. I don't care what the tuning school says it's not always true.
Not doubting you at all. You and all the others are getting me to research a lot of things and that is one that I came across. I will take the valve covers off and check things out on Sunday as tomorrow I will be out for most of the day coaching youth football. Quick question though will valve float just happen in drive/gear or can it also happen during revving? This will let me know if I should turn the car on and record the valvetrain and rev it up.
Not doubting you at all. You and all the others are getting me to research a lot of things and that is one that I came across. I will take the valve covers off and check things out on Sunday as tomorrow I will be out for most of the day coaching youth football. Quick question though will valve float just happen in drive/gear or can it also happen during revving? This will let me know if I should turn the car on and record the valvetrain and rev it up.
You can't see valve float just by looking at springs, well unless one is broken which is always a possibility I guess but it happens at higher RPM especially on turbo cars with the hot side backpressure on the exhaust valve. I would measure the installed spring height and calculate how close to coil bind you are at peak lift, you may have to shim the valve springs to get a higher seat pressure, etc. Might not be a bad idea to measure your current spring seat pressure at the current installed height as well to see if those valve springs are good.
You can't see valve float just by looking at springs, well unless one is broken which is always a possibility I guess but it happens at higher RPM especially on turbo cars with the hot side backpressure on the exhaust valve. I would measure the installed spring height and calculate how close to coil bind you are at peak lift, you may have to shim the valve springs to get a higher seat pressure, etc. Might not be a bad idea to measure your current spring seat pressure at the current installed height as well to see if those valve springs are good.
So would just revving it and watching idle and listening to the valvetrain help me to single it out to know for sure it is that? I just want to be 100 on it before spending money. But I will have to get the tuning part cleared up before that right? Take it in steps... Speaking of steps if you were going to tune a car how where would you start and go to before finishing the tune? Would the VE table be the last thing to be adjusted? I don't know jack on tuning so the steps on would help for my knowledge.
Originally Posted by tech@WS6store
Did you check fuel pressure under a load in the upper rpms?
Id check for a voltage issue also if it were me.
The tuner records the gauges as he is doing pulls and he said it was all good. As far as voltage I don't know, I have just the stock gauge that isn't precise but it normally stays somewhere to the right of center.
Seriously? I've personally seen turbos eat themselves, new BWs and Precisions because a charge pipe came off and the owner didn't realize it. This is nothing new and it has nothing to do with not being the 80s.
Turbos don't spin nearly as fast without boost. They need the exhaust volume. Resistance on the compressor wheel isn't created until positive pressure is created. Until then, the vacuum created is actually helping (somewhat) to spin the turbo up even faster.
Which basically means that every every laggy turbo setup out there is effectively running with the charge pipe disconnected until it builds boost.
Precision turbos blowing apart is nothing new.
The new borg turbos have sensor ports in the compressor housing for turbo RPM.
Guess what? They don't spin NEARLY as fast without boost. Data is out there.
So would just revving it and watching idle and listening to the valvetrain help me to single it out to know for sure it is that? I just want to be 100 on it before spending money. But I will have to get the tuning part cleared up before that right? Take it in steps... Speaking of steps if you were going to tune a car how where would you start and go to before finishing the tune? Would the VE table be the last thing to be adjusted? I don't know jack on tuning so the steps on would help for my knowledge.
No you need to pull a valve spring and check installed height, seat pressure, etc. At that point if there is room to go or seat pressure is a bit low I would be shimming the springs and trying again on the dyno to see if there is any difference.
As far as finishing the tune I have no idea what the reported a/f ratio was or anything like that since the graph doesn't show it. However If somebody brings me a car that has a mechanical issue I tell them it needs to be fixed before anything else happens and I stop right there. Lots of tuners have a different order they like to do things in but that VE table is pretty rough and since that directly controls fueling and estimated airflow/load it obviously needs to be dialed in pretty early on before adding timing.
Turbos don't spin nearly as fast without boost. They need the exhaust volume. Resistance on the compressor wheel isn't created until positive pressure is created. Until then, the vacuum created is actually helping (somewhat) to spin the turbo up even faster.
Which basically means that every every laggy turbo setup out there is effectively running with the charge pipe disconnected until it builds boost.
Precision turbos blowing apart is nothing new.
The new borg turbos have sensor ports in the compressor housing for turbo RPM.
Guess what? They don't spin NEARLY as fast without boost. Data is out there.
Yes that's true most turbo failures from over spinning occur due big boost leaks, etc but I would still never suggest just disconnecting a charge pipe and making a pull and no turbo manufacturer would either. I'll be sure to tell the next turbo manufacturer though that I read it was OK on the internet to do so when it needs to be sent back for a rebuild. LOL
A valvetrain has no idea what load the engine is under. It DOES, however know full well how fast it's going AND whether or not it can hold up at those speeds.
Valve float is also related to cam ramp design. A correctly designed and engineered cam will float the valves later than a cam not so well designed, with the same springs
Okay so I managed to get some graphs of the last runs before I made this thread. I am obviously using hydraulic lifters and have read that with valve float it would run terrible after it floats because of the lifters get stuck in a sense would making back to back runs without giving them time to rebound be possible without any changes from before it floated? Also ran it in first gear all the way up to redline without any issues and it pulled all the way through with no hesitation or stubble. Next I will try recording it and making a pull in boost to see if I notice anything. The 409.98hp graph was the last one he did after he played with the tune to smooth it out. He just put the 450 tune back in because he couldn't figure it out. Could the problem with the tune and running lean cause some issues? He doesn't use his innovate and goes off my wideband but I have been reading also that my wideband might be in a bad position as it is before the turbo and not after so I might be off a couple of points if what I read is true. combined first one I think second one final one of that day
What springs?
I think you are thinking way too complicated.
Test a few things at a time but dont change anything yet.
Test voltage at battery at alt and at fuse box
Test fuel pressure through whole run
Those 2 will get you alot of info that can cause issues also.
What springs?
I think you are thinking way too complicated.
Test a few things at a time but dont change anything yet.
Test voltage at battery at alt and at fuse box
Test fuel pressure through whole run
Those 2 will get you alot of info that can cause issues also.
Just checking possibilities as I run though the checks. I will get on testing the voltage because that is easy enough. I also have 2 fuel gauges so that will also be easy just have to record it so i can pay attention to other things. Cam specs are duration 232int 240exh lift .595int .608exh lift. Springs are patriot dual golds (.650 lift) probably 4-5k miles maybe less on them. The car got built and tuned in GA and drove across country to NV with no issues. No high revs the entire drive and went to the dyno here in town with the issue at hand so the car has pretty much only seen that and hasn't been driven much at all
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Slideshow: The controversial Ferrari F6 swaps its original flat-12 for a Corvette Z06-derived LT4 V8 and sends power to four rear wheels through a custom-built drivetrain.
7 Most Reliable High-Performance Engines GM Has Ever Built
Slideshow:These GM engines didn't just make huge power, they survived abuse, boost, track days, and six-digit mileage with a reputation for refusing to quit.
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Slideshow: From wobbling harmonic balancers to failed EBCMs, these are the issues that define long-term C5 ownership and what repairs typically involve.
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Slideshow: A modern Camaro transformed into a retro icon, this limited-run "Bandit" build blends nostalgia with brute force in a way few revivals manage.
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Slideshow: Cadillac didn't just crash the high-performance luxury vehicle party, it showed up loud, supercharged, and occasionally a little unhinged...
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Slideshow: A one-off sports car that looks like a vintage Italian exotic-but hides a C6 Corvette underneath-just sold for the price of a new mid-engine Corvette.
