Flat spot then sudden power at high revs
 

I've added a supercharger to my car and took it to the dyno yesterday to get the map dialled in on the DIYPNP running firmware 3.0.3 t

It runs very well apart from a massive dead spot in the rev range between 5 and 6 k rpm but as soon as I hit 6 k it suddenly comes to life again and pulls like a train. I do have what appears to be a boost leak as the MAP starts to drop around 5 k but it does it fairly linearly.

The tuner watched the dials whilst I gave it wide open throttle on the road and said that intake temps, ignition timing and the afr's all appeared rock solid throughout the run with no sudden drops to indicate the ecu was pulling anything.

The car is a 96 with a supercharger, intercooler and 440cc injectors. I've attached my msq adn i'll try and get a log of the issue as soon as I can.

Any ideas are really appreciated

Adding the log files

Oh that's easy to solve, get rid of the supercharger. Is your belt slipping? on your log the higher you rev KPA decrease

do anything with the timing belt recently?

y8s, i've not touched the timing belt since I got the car when it was replaced.

buffoon01, if you've got a turbo kit you can ship out to me for an extended test then i'll happily give it a go :)

It's sounding more and more like it's something mechanical rather than the squirter that's causing this. Either belt slip or a boost leak. The other thought is something like the coil pack or HT leads dying. Would they cause this sort of effect with the flat spot then sudden pick up?

That's what I'm seeing too.

Could be bet slip but then why would the car suddenly pick up at 6k rpm? Also any good tell tale signs of slip?

It doesnt. Look at your log; KPA decrease past ~5.5k, and does not go back up. I think is your belt is the same tendency in all the gears, and at about the same RPM range.

I'm having a similar problem, and I'm turbo'd. I've checked tooth and trigger logs expecting to see some issues there from what I'd read in other posts, but no luck. I have no idea whats going on here.

Looking at your log I see a spot where your PW looks choppy in the 5-6k rpm range.

My problem seems to line up right with being under WOT and over like 9-11psi. Part throttle upto 11 psi seems no problem, but WOT and it loses power just like you describe and then around 6k-6.2k if you hold it down it'll pull like a train out of no where.

I plan to try a different set of plugs tonight, but I don't see this helping much really, just another attempt to diagnose it.

Also - my experience is street tuning, I have not yet had the chance to see a dyno with the car.

Checking up... Any further results GrahamA?

I changed my plugs, old plugs looked over heated and run rich. Possibly because I'm pushing too much psi for my setup, but I suspect the heat of from running lean in the area of power loss due to the fact that I have not yet setup my accel enrichment.

I'm still trying to get a better understanding of the MAP vs TPS enrichment settings and the X-Tau enrichment. I believe that is the problem I am experiencing. So, next week while my family is out of town I plan to spend some time fine tuning my warm up and the accel enrichment.

Well I have found out that i'm getting slip. Lot's of dust around the charger nose. Also someone on the msextra forums pointed out a dip in my spark table around the point where the flatspot comes in rising up to where the power comes back. I think i'm dropping boost down to 0.4 bar at the same point as this dip in the spark table then the pick up i'm feeling is the timing coming back whilst still at 0.4 bar. Not had a chance to test this yet but i'm about to upload the new spark map and re-tension the belt then give it a run tonight.

Turbobarber, i'd say if you're running 11psi you'd be wanting an intercooler of some sort. What are your intake temps like? I think i'm maxing out at 40 degrees centigrade on a hot day with my cooler.

I have my plans for something in place of the intercooler, but I doubt anyone here will approve it so they'll just have to wait and see, holding off their disapproval for post success. I sometimes like to think that I think outside the box, but sometimes find myself a wee bit too far outside lol.
My current air temps I couldn't tell you because I placed my IAT prior to the water injection nozzles, which reads as much as 300+ degress at 12+ psi. But worry not, this is NOT the true air temp going into the head. Nozzle 1 is a 1.0 GPH spraying 3 inches after the IAT and nozzle 2 is a 3.0 GPH spraying 3 inches before the TB. I would very much like to know what the final air temp is inside the manifold tho...

Anyway I'm about open a new thread on this. I believe I found my problem - the solution resulting in both my clutch slipping and the turbo spooling so hard and fast it blew off my bypass hose. EAE.... Oh man... Whoa. Totally different beast. Perhaps this is because of my poor tuning skills, or my injectors I'm not sure, but this has truly made the difference. There is more tuning in to be done, and next week's relocation of my IAT will require retuning my VE table. I've knocked out my 5k-6k problem all together. Smooth power to the redline - Given the clutch holds up. Yay time for another new clutch!!

Hope this helps... I would just give it a try... enable the Enhanced Accel Enrichment and let it rip. My experience with it today was it did cause a poor response/bucking when snapping from part to full throttle(something to tune in later), but even a quick smooth roll into WOT yielded smooth full power all the way through the rpms.

I think I've found something, here's an image of a log I did the other day,
Attachment 196315
The mark lines are just before a 3rd gear pull and just after the power kicks back in. During the flat spot I can see that the Pulse width and duty cycle are bouncing around like mad.
There also seems to be a dip in the spark advance at the same time. I think this is because i'm hitting 160kpa and rows in my spark table for 128,154 and 174. The rows for 128 and 15 are reasonably close but the 174 row drops by 3 degrees across most of it. I think when I get boost up to 160 it starts to use values between the two higher rows, meaning it drops where as when it's coming up to boost it's using the 128 and 154 rows and keeping it fairly level.
Attachment 196316
I'm thinking I need to ditch the 200kpa row and add in a 165kpa row then interpolate the figures to generate that row (to be honest i have no idea how interpolation works so a bit of help here would be great)

Turbobarber, i'll have a look at the eae and give it a go, can't lose anything by it :)

what about detonation possibility?

a 3 degree change in timing wont make the car feel flat. a 10 degree change might.

The guy on the dyno said he didn't hear any det throughout the runs he did. I think the cause of the flat spot is whatever is causing this noise in the pw and duty cycle graph lines. I'm pretty sure it's something to do with the ms as I had a similar flat spot whilst n/a but not as pronounced.

I think your problems stem from the fact that you're using percent baro for your fueling algorithm instead of speed density.

Finally had a chance to switch to speed density and it definitely feels better but I'm still not getting a smooth power delivery. Is it just a matter of re-dialling in the fuel table or do I need to make other changes?

Yeah it's going to need to be tuned.

Should I just let ve-analyze do it's thing on the current table or would I be better off scrapping that one and starting again with the one from the base maps?

keep same map but you still should do something about the belt slippage after 5K.

Just upgraded to MS2, and I had some ignition settings wrong that was preventing me from revving past 6k. Anyway I cleared that up and I'm noticing I have the exact same issue. Pulls great till 5k, goes flat, and then takes off like a bat out of hell at 6k again. Obviously it's not belt slippage since I'm running a turbo. I need to log it and post it. May or not be the same problem as you.

exactly the same happens to me too (MK2.5, MP62 supercharged)...
the boost drops suddenly at about 4600rpm and then comes up again at 6k rpm...it is definetelly not belt slippage, because if it was, boost wouldn't come up again...I have attached a 3rd gear pull log, and the spark table I am running

All my new logs show fairly constant boost (tightened a few bolts and not getting any more dusting under the bonnet)
I've tried a run with the basic spark table from diyautotune's base map and had the same result. The switch to speed density has improved it but there is still this kick at 6k rpm.

ever thought about leaning it up? your VE table goes 7% richer in boost between 5400 and 6000 RPM, you logs looks like it dips into the high 10s for AFR. You shouldn't need to run so rich with a SCer at 8psi. I don't even run that rich at 15psi.

One big difference in my case is that although there is a boost loss in the logs, I don't really feel it...So I talked over the phone with our MS guru here in Greece (Dimitris aka Reverant), and he told me that under certain circumstances there is a chance that the boost I see on the logs is "fake"...so I will check with my boost gauge to see if there is a drop there too....

Ve-analyze has been trying to lean it out for me. Trouble is I think I'm so rich that I'm burning fuel in the exhuast manifold and cooking my lc-1 which means an aborted run. I think I'll try a leaner map to start with and build up the revs slowly and let autotune do it's thing.

Stav was your spark table set-up at a dyno or road-tuned? It dials in alot of timing around the peak torque curve area and then pulls timing towards the red-line when you could actually be adding it in lightly. The log shows a blip in boost exactly where your timing advance peaks. Have you tried smoothing your advance table?

Also your MAT's look heat-soaked? It reduces as you do your 3rd gear pull?

the table was set-up on the road...and to be honest was meant for my previous setup (JRSC at 11psi)...I did play a lot with fuel and afr tables but I didn't touch the spark table after I fitted the MP62 2 weeks ago...I am not that familiar with tunerstudio yet :) :) :) :)

As for the temps, i didn't notice that before...I did the pull right after I spent a minute or two waiting to pay the tolls, so I guess that might was the reason for heatsoaking (btw I forgot to mention that I haven't currently connected the fmic, as I need to fab the piping)

Had another run today and started with a much leaner table but was still suffering the same flatspots and surges I then switched on the enhanced acceleration enrichment and the car was transformed. Smooth throughout the rev range, no sudden surges in power and just damn good fun to drive. Need to work on the eae settings as it will bog down now if I floor it in too high a gear but otherwise a great result.

went out yesterday to check boost on the gauge...there is a drop there too...so it seems that its not a fake signal....
I read somewhere that a faulty PCV can cause that effect...leaking in relatively low rpm and the sealing (somehow!!!!) off at higher rpms .... has anybody heard anything about that before??
In any case I ordered a CUSCO oil catch can yesterday, which I am going to install along with a one-way valve and a new PCV valve ( i was lucky to find the can brand new for only $32 :) :) :) )...

Nice, right?? So... I would watch your tpsDOT(and mapDOT if you use blended enrichment) in your logs and try to taper down that flooding that occurs when you snap on the throttle. I pulled out some of the PW added by tpsDOT and the result was improved throttle transition, but with my clutch slipping now it's going to be near impossible to finish tuning until I get another clutch.

That said - I'm guessing you're happy with your VE table? It should be fine tuned before proceeding with the AE and EAE. There won't be much you can do about the power loss in those rpm ranges without it, but get it as close to the AFR's you want as possible, then move on to messing with the tpsDOT/mapDOT and the EAE. My results with the EAE involved no modification of the EAE settings themselves.... They seem to be working fine, for now.

Hope this helps


Otherwise tomorrow I'm going to *attempt* to braze my IAT bung onto my intake pipe.... should be fun lol just finished brazing up a throttle mount plate and tube fitting for my monster mower, so I've got some short practice in :D

I had to alter my Stuck-To-Walls table significantly. The Sucked-From-Walls, not as much, but I did need to alter the rpms corrections for it.

I managed to eliminate my flat spot this morning by reducing maximum dwell to 3.2 from 5.0.