Is this valve float? Bad maf placement? bad maf? backpressure?

[kleistang]

So I've been fighting this power drop that happens at 6500rpm and then climbs backup up. its around 600-800rpms in where the power drops about 100hp.

What I have gathered so far is that yes, the camshafts i am currently running are way to aggressive (compcams 191460) the overlap while the cams are parked is are 25.5 degrees, and advancing the evc to the max i can which is 20 degrees while setting the intake to 0 helps a bit and the engine does pick up power right after that gap. I am putting the stock cams back up assuming the problem is the valve float being caused by excessive backpressure thanks to the extended cam duration. I spoke to a couple of shops who agree that just by looking at the cams they are way to aggressive, one of them was pretty confident that valve float is the problem and that the jpc turbo kit I have does suffer from backpressure issues. I was recommended to switch the exhaust cam for the factory one and the intake side for the custom l&m. I will be switching them to stock before I attempt to use another aftermarket cam. I had such a bad experience with every company I've reached to get bare minimum recommendations or opinions. Specially comp cams lol I have 2 sets of cams ($3k+) I bought from them the stage3 currently in the car and a stage1 to test something milder.

Anyway here is my current tune. I trashed my old tune completely, created a brand new one and had pretty much the same results. I re-scaled the maf, played with the cams while having little understanding on them. Continued trying after I learned enough to know what could be happening and proof that closing the exhaust as much as possible helps but just not enough.

If you have any recommendations please share. Thank you. If I remove everything and leave the maf/period on the graph I can zoom in and see the maf acting weird at that point.

2013 gt
built block
stage3 comp cams 191460
tfs valve springs
manley valves in/ex
jpc turbo kit
cd converter
ds
etc...

[murfie]

Usually the RPMs are effected to the point they do not keep climbing from that. It definitely doesnt stop happening higher in the RPM range. I did just read about a similar probalem someone had with livernois springs and switched to manley and the problem went away. So don't rule it out. 209 LB/in for the TFS compared to 322 lb/in of the Comp cams is also more evidence its valve float.

Transmission doesnt look like its slipping and that was my last question in the previous post.

I dont think this would cause your drastic HP loss, but looking at your MAF I am seeing its good until 120 period. Then the MAF airflow and frequency do not follow each other as they should. I think your Air flow values from 120 to 97 period are too aggressive. At 108-103 you have a 8.5 Lb/min jump this is the weird behavior you are seeing.

TransKL.PNG

[kleistang]

Yeah the maf acts weird around there, but honestly i compared the difference in numbers on those cells to the cobrajet and roush files and scaled using somewhat the same % difference between cells while trying to keep accurate maf/lbs numbers from previous logs.

Lol I think I was high or drunk the first time I read this thread lol after this I remember I ordered the tfs stage1 think it was going to be enough, since I was not doing anything crazy at the beginning, then somehow I ended up getting a deal on those cams which were not on the original plan (tfs1, racing intake valves, hd exhaust valves and stock cams) so after reading this thread again and making sense of what both parties argue and understanding as much as the tuning process vvti control, valve timing as I do now, it seems like I mixed shit with hot sauce made a cake lol.

The comp cam exhaust duration is advertised at .50 but the real closing of the exhaust happens at 20.5 degrees atdc so closing the exhaust 20 degrees earlier is not enough to close the overlap completely if needed at higher rpms. the original overlap of the cam at .006 is 20.5 degrees leave the intake parked and advance the exhaust 20 we end up with 5.5.


I bet if I take the exhaust camshaft and exhaust tf stg1 springs out and place the factory cam, tf stage2 springs on the exhaust. Leave the intake side alone limiters and all It should be able to spool the engine fast enough, rev high and get the 1000hp. on the same turbo/kit

Or maybe even using the compcam stage1 exhaust side even thought the duration is a bit more aggressive than stock I'd gain a bit more lift, If I remember on the stage1 the overlap was 11 degrees parked so the 20degrees on the limiter would probably be enough to completely close the overlap if needed. I'd have to do the math of mixing the stg3 intake cam with the stg1 intake cam.

It's funny I am having all the problems on that thread, I have an aggressive cam, mildly upgraded springs and also have a jpc kit. lol

Check this pic out, it looks like the rpm is bouncing.

RPM.PNG

[murfie]

yeah the more I read about it you seem to have valve float. Sounds like you have a plan to fix it while getting a more optimized cam for your setup when you start turning the boost up. The thread I read was actually someone crediting Shaun for fixing the problem as soon as he heard what springs he was using.

[kleistang]

I talked to him, and He sounds really confident on what the problem is. He recommended to swap the exhaust back to the factory one and change the intake side for the L&M re grinds, which sounds good since you get to keep full motion of the vct. I would like to confirm this before I actually purchase another set of cams already having the stg1 and 3 + factory. With the cam card I should be able to get the valve event timing and calculate how much overlap there could be at specific valve events to work the vct tables and spool the turbo as fast as possible. I believe it was him who designed the L&M camshaft, Honestly after speaking to so many places including jpc, comp cams, ford racing (which was kind of cool) he sounded brilliant and not the kind of guy that works everything on a trial and error type way but more of a meticulous way.

[MJMunoh2011]

The part number you posted I think would work fine for your application. With the springs you have do you know your installed height and distance to coil bind? Being those are the NSR cams you may be getting low open load. May need to shim the spring up some. If its too far from coil bind it won't have as good of valve control at RPM and on a boosted car that will kill power quickly. Also are you sure your phasers are staying in control? Its a good thing to monitor as I don't know your exact setup but the phasers can struggle to maintain the same sweep under boost with the claims poor boost to back pressure ratio you may have.

[kleistang]

I am honestly not sure, The machine shop guy just replaced them I don't think they measured anything as they were supposed to be drop in springs. as per the cam control, they have seem to follow as commanded but going through my logs I do remember at one point playing with the feed forward duty cycle, I added 20% and the dynosheet did seem better at that time, I gave up quick on keep adjusting it since the guy on the dyno always tries to help since he has experience tuning but mostly haltech and other cars so he has learned a bit about this cars kept telling me we did not have to touch those blah blah. Anyway with the 20% duty cycle the rpm looks less bumpier, the problem always seems to happen at 6300-7300 rpm after that it gets better which is weird.

My last runs were with a 10% on the ffdc tables I am attaching a pic, these pulls do look better than previous pulls without touching them, I don't have the dyno sheets right now but the power line did look better too when i did it before at 20%+ and honestly the gap of power loss before was like 100-140hp to like 70 I have to get the sheets to compare. 10%dc.PNGwith20%dc.PNGwithout20%dc.PNG

[kleistang]

How much can we add on those tables? perhaps I should try at least on the street and see how the rpm reacts adding more to those tables.

[RickClarke23]

I am having a similar issue. After talking with a friend who builds a lot of Coyotes he has had this happen before on the single turbo kits that still have stock manifolds. Does yours? The issue is backpressure. He instructed me to upgrade to Kooks Shorty headers and it will fix the valve float issue

[kleistang]

I am having a similar issue. After talking with a friend who builds a lot of Coyotes he has had this happen before on the single turbo kits that still have stock manifolds. Does yours? The issue is backpressure. He instructed me to upgrade to Kooks Shorty headers and it will fix the valve float issue

I do have factory headers, I really have not measured the backpressure but this is what people keep saying when I mention the cam's duration. I thought about doing that, I figured if backpressure is causing the valve float I could add more volume to the piping by adding shorty headers and increasing the piping size somewhere as well as swapping the turbo out to something with a bigger ar. I was told it wouldn't make a difference and it would make the car lag, but honestly i think if that could help the valve issue, you can take advantage of the bigger cam and vct to spool quicker then close it at the end. I guess different people suggest different things.

Whats ur current setup. I've found a couple of threads online that run into similar issues even with different setups/engines/cars but none of them really have an answer to what fixed the problem. I figure they got rid of the car or something lol.
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[kleistang]

Murfie, I updated my maf settings with the data on the last runs I made. You are recommending to to update that side or the period numbers to be closer to each other ?

[murfie]

Apply to the Maf lb/min value side. I know once you figure out the drop you are going to up the boost and need the period range.

You have your enrichment rate high so your fuel trim error is being applied slower. Your actual lambda is not staying on your commanded because of this.

I was just looking at your LB/min against your frequency. they should have a direct relationship. on a comparable scale they kinda do up until 120 period then the lb/min slopes up faster than frequency does. It may have something to do with the bank to bank difference going away throwing off what you are applying to the curve. Did you ever modify it to just use one O2 sensor with the single turbo setup?

[RickClarke23]

I do have factory headers, I really have not measured the backpressure but this is what people keep saying when I mention the cam's duration. I thought about doing that, I figured if backpressure is causing the valve float I could add more volume to the piping by adding shorty headers and increasing the piping size somewhere as well as swapping the turbo out to something with a bigger ar. I was told it wouldn't make a difference and it would make the car lag, but honestly i think if that could help the valve issue, you can take advantage of the bigger cam and vct to spool quicker then close it at the end. I guess different people suggest different things.

Whats ur current setup. I've found a couple of threads online that run into similar issues even with different setups/engines/cars but none of them really have an answer to what fixed the problem. I figure they got rid of the car or something lol.
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its a car we built and are tuning on. Built motor stock compression 11:1, Hellion Single turbo kit. Stock Cams, 10lbs to start on E85. Stock Manifolds, car has valve float past 6300rpm on the dyno. I'm going to switch out the manifolds to kooks shorty headers as 2 people with single turbo coyotes who had similar problems fixed it by doing this.

[lt1z350]

I just talked to my buddy about this on his setup. Twin turbo hellion kit 2013 5.0 same issues were happening and found it to be back pressure on the exhaust side. Said alot of guys are adding big exhaust springs to mask the actually problem of boost/back pressure holding the valve open acting like valve float in higher boost. What he did was port the exhaust side of the head. Left intake alone so he said but sure probably cleaned it up. The exhaust side he opened the port to a large d shape and not only did it fix his issue the car now makes over 1000 whp. Guess this is a pretty big problem on higher boost on the 5.0. He is an engine builder and head porter by trade so took time to diag the actual problem and got to the source rather then bandaid it with a huge exhaust spring. One of the guys I race with and know was fighting getting this car over a certain psi but now it's unreal. Think 9.50s @152 last time out with a 6r80. So all in the heads and limited flow.

[LavaRed50]

A lot of the T4 housing small turbo kits have very bad valve float issues with the stock cams, not to mention with larger cam profiles.

[kleistang]

Apply to the Maf lb/min value side. I know once you figure out the drop you are going to up the boost and need the period range.

You have your enrichment rate high so your fuel trim error is being applied slower. Your actual lambda is not staying on your commanded because of this.

I was just looking at your LB/min against your frequency. they should have a direct relationship. on a comparable scale they kinda do up until 120 period then the lb/min slopes up faster than frequency does. It may have something to do with the bank to bank difference going away throwing off what you are applying to the curve. Did you ever modify it to just use one O2 sensor with the single turbo setup?

I tried running a single o2 but it was running kind of rough and acting up, maybe if I spend more time dialing it in that way it will get better, however Shaun said really confident that I should get rid of one of the sensors and place the other one on the downpipe. he says that the kit having the o2s on the factory location reads way to lean and that is most likely the cause of my first engine failure.

I think im gonna add that to the list of changes when I tear down the heads. You are right I always see my a/f go a bit richer than commanded at higher rpms, it also happens right around the same time the power drops.

[kleistang]

its a car we built and are tuning on. Built motor stock compression 11:1, Hellion Single turbo kit. Stock Cams, 10lbs to start on E85. Stock Manifolds, car has valve float past 6300rpm on the dyno. I'm going to switch out the manifolds to kooks shorty headers as 2 people with single turbo coyotes who had similar problems fixed it by doing this.

Bro! if that helps let me know. Jpc keeps saying on those threads that the springs should be installed correctly by putting shims on them and it makes sense too. Like MJMunoh2011 says the spring might be there and it could be a higher rate than factory but if it is not shimmed properly you loose some of its pressure. I also think the forward feed dc plays a big rule and needs to be tuned properly, adding 10% to the table made it better, I added the boss302 data a couple of days a go and the car feels more solid. I have not put it on the dyno, at this point im tired and kind of want to get everything that could help done at the same time. lol I already ordered the shims, I have the stage1 exhaust which i think im gonna use. Your idea of the shorty headers sounds promising, plus if I get a set of heads i might get them ported as well. If i have problems after that I will burn the damn thing haha.

Keep me posted if the headers make a difference I'd like to know.

[kleistang]

I just talked to my buddy about this on his setup. Twin turbo hellion kit 2013 5.0 same issues were happening and found it to be back pressure on the exhaust side. Said alot of guys are adding big exhaust springs to mask the actually problem of boost/back pressure holding the valve open acting like valve float in higher boost. What he did was port the exhaust side of the head. Left intake alone so he said but sure probably cleaned it up. The exhaust side he opened the port to a large d shape and not only did it fix his issue the car now makes over 1000 whp. Guess this is a pretty big problem on higher boost on the 5.0. He is an engine builder and head porter by trade so took time to diag the actual problem and got to the source rather then bandaid it with a huge exhaust spring. One of the guys I race with and know was fighting getting this car over a certain psi but now it's unreal. Think 9.50s @152 last time out with a 6r80. So all in the heads and limited flow.

Yeah, I think that sounds about right, I honestly thought it would not do anything to port the heads at first but I am regretting now, It could have save me some headaches. Do you mind asking your friend how much a port job as you mentioned would cost me.

[veeefour]

OP, ever figured this out? Same problem here, Comp Cams and 6500 power loss.

Nothing in logs but my ass can feel it - runs like a bat form hell but that dip around 6500 rpm prevents my brain from going higher with boost.

Leaning towards too aggressive cams - might swap the stock ones back or upgrade the vale springs.

[veeefour]

If you ever wondered how the valve float looks like just follow the violet IN line. Classic...those Comp Blower Cams are just too nasty - need a waay harder springs. 7psi all good, 10psi no go LOL

Float.jpg