Higher RPM/Boost Hesitation

[cammmy]

Hi All

Just converted my Lotus Esprit to MS3/X and am now trying to use VEAL to dial in my fuel table a bit before the car goes to the dyno in a couple of weeks. Started rolling into higher RPM cells and have struck an issue. At around 4,000rpm it hesitates, almost like a fuel cut. I've been looking at my datalog and I'm a bit stumped. I've attached my MSQ and data log but here are the basics.

'98 Esprit GT3
2L 4 cyl motor
GM DIS ignition
Sequential injection, 4 primaries, 2 secondaries. Primaries are low Z running with a resistor for each injector. Secondaries are high Z.

I can't see an option in tunerstudio about the number of secondary injectors; so I've assumed it thinks there are the same number as there are primaries. I've set the injectors to half of their actual flow rate and 1 squirt simultaneous.

As the logs shows, it's running very rich at the moment. I took the tables from an MR2 turbo and brought back the timing and increased the fuel a bit. I'm now trying to get VEAL to get the VE table in the ballpark.

The two points of interest in the second log are 8660.766 and 8802.816. At these points I'm not using massive amounts of throttle but am letting the RPM climb. At about 4,000 it hesitates and goes lean. I don't see why it would be doing this. Overboost is set to 210kpa, which I'm not hitting, rev limiter is set to 7,400rpm over 70 degrees C, which I'm over. It seems like it almost deciding to fuel or spark cut (although there's no backfire when it happens). I tried disabling sequential injection but still no joy.

Has anyone got any ideas? The car rev'd out fine on the stock ECU. Could it be a rich mis-fire or something?

Thanks

[lotus23C]

May be nothing, but there are some big jumps in your Ve table, try smoothing it out manually. Might help.

[cammmy]

Cool, thanks. That's probably where VEAL has brought down the cells I've hit. I'll go through it and dial the others down a bit manually.

[cammmy]

Do my map readings look funny to anyone? It seems whenever I'm cruising at 2,000-3,000RPM with about 10% throttle, it's reading 90-100KPA? Seems high?

The car has ITB's fed from a plenum from factory. The manifold has a common rail across all runners that the MAP sensor reads from. I've used 3mm ID vacuum line from the manifold to the MS. I'm running a MapDaddy4 sensor. I was pretty careful to get a good seal on everything but I'm not a fan of the mapdaddy sensor TBH. It's not barbed so the vacuum line comes off really easily. I've used to 2 cable ties to try and secure it as tight as possible. Should I be breaking out the superglue to try and seal the hose onto the barb?

Would that explain what I'm seeing?

[cammmy]

EspritGT3.msq

Okay, some further investigation this evening. Took the ECU out and connected it to the stim. Blew into the MAP hose and clamped it off. If there's a leak there, it's a slow one. It was reading maybe half a kpa less after about 20 seconds. Sucked the air out down to about 30kpa and again, no real loss after about 20 seconds.

Went for another drive. Tried to get more examples of the issue and also not lift off the throttle quite as quick, first result is here:

2016-07-13_20_short.msl

I noticed the issue seemed to be when it got to about 140kpa at about 4000rpm so I drastically lowered the VE from the 100-180kpa cell range but there was no difference in AFR and the same thing happened.

2016-07-13_21_short.msl

EspritGT3.msq

Finally I disabled the staged injection and tried again. I tried to roll into the problem area as slow as possible, it seemed to go a little higher (about 170kpa) but still the same thing. I can't add another attachment in this post.

So I've got a few things I'm wondering about:

Lowering the VE to well below 100% even under boost hasn't changed anything. It's still pegging the o2 to 10.0 before mis-firing.
Lower RPM doesn't show any issues (even the same boost level), it's only at 4,000RPM+
It doesn't seem to be related to staged injection (which comes in around 4,000)

Could it be an ignition issue? Running so rich it's fouled the plugs?

On the weekend was the first time I started trying higher throttle angles. Got a few in up to 5000+ at higher throttle okay then it backfired and went lean. I back out, and limped it home. The fuel pressure reg adjuster had come loose and dialled itself down. I've adjusted it back and checked it's still okay. It runs fine other than this issue.

Any assistance appreciated. I'm booked in for a dyno session at the end of the month and they're quite expensive, so hoping I can get there and have them start mapping straight away rather than trying to sort this issue.

[cammmy]

last data log

2016-07-13_21_short2.msl

[hobieboy]

Looking at the data log, you are running very rich - even at "cruise" AFR in mid-12's. Maybe it is an ignition blow-out situation from running too rich?
Definitely should pull the plug to at least get a sense of how wet is it.

[turbo conversion]

Can you post an msq of a warmed up engine just idling for a couple minutes?

David

[cammmy]

Thanks, I'm not at home tonight but will get another log tomorrow.

It idles fine, I can adjust the VE tables in that area to get it wherever I want (it idles at 50ish kpa - 1,000rpm). Also, VEAL is able to get the cruise areas to match my AFR target. It's the higher RPM and boost I'm struggling with and can't seem to affect. I dropped VE in boost quite significantly on the second run but it still went super rich.

I think the reason it's so rich at cruise is that it's often showing as 90-100kpa. My AFR target at 100kpa is 12.6 and at 87kpa it's 13.4, so VEAL does get it to those targets quite well. When cruising at very low throttle angles, I do see it hovering around 13.5 - 14.5. I'm not sure why the pressure would be so high at cruise, I'd expect it to be wanting to accelerate at that MAP but I don't think there are any vac leaks.

I'll pull the plugs and have a look tomorrow as well.

If it's worth anything, my pressure reg is 1:1 and referenced from the manifold where the factory unit was and I've set it to vac references in TS.

I appreciate the replies. I'm currently trying to work out whether I have a hardware/software issue or whether it's just a lack of experience on my part.

[turbo conversion]

Is your engine some what stock except for the turbo or is it highly modified?

David

[cammmy]

Turbo is stock, exhaust is all custom including manifold. Cam timing has changed slightly but that only puts them back to where they were designed to run (they re-timed them to increase reversion to get past emissions regs rather than introducing EGR). Induction before the turbo has been improved a bit but I wouldn't say it's drastic.

cams are both 272* with 104* MOP and the car is on ITB's from factory

[turbo conversion]

What rpm and kpa did the engine idle at before the conversion?

David

[cammmy]

Unfortunately I don't know. I'll ask around the esprit forum to see if anyone has any numbers.

[cammmy]

Seem these don't pull a lot of vacuum:

http://www.thelotusforums.com/forums/to ... uld-it-be/

"I see about 0.7 bar MAP at warm idle."

http://www.lotustalk.com/forums/f164/wh ... s4-115329/

"Upon messing with an ignition problem a while back I found approx. that same reading, I think its normal, about 10 in on the vacuum gauge. I at first panicked and thought that was low, then did a search and found somewhere that its about normal."

So to address the rich running under boost issue. Should I just keep bringing the cells down until I can see it's not pegging the o2 sensor at 10? How does the VE table work? I would expect it to be a reasonable approximate of the engines actual VE. Seems odd that something running under boost at peak torque RPM would have a VE below 100%, unless I'd spec'd the injectors wrong? I have new injectors though which came with a flow chart and dead time info, so I don't think that's the case. The fuel pressure is set to match the flow chart.

[turbo conversion]

The cams must have a lot of over lap with that kind of idle kpa.

As far as I can tell your AFR map looks pretty good, but the VE table I think is your culprit.

As far as the VE table my VE table is tuned under 100 and it has not been an issue for me.

As you I am using include AFR so my rough tuning is done on the AFR map.

I then fine tune and blend the AFR with the VE table for accurate afr with very smooth transitions.

David

[cammmy]

Okay brilliant, thanks. I won't panic then.

I'll pull the plugs and give them a clean, then start tuning the problem area down until I can see it have an effect. I'll then try to get the rest of the table to match and let VEAL take over until it's at the dyno. I really just want to make sure I don't have a fundamental issue that will waste dyno time.

When I was searching for vacuum figures, someone else said they had injectors that make everything far too rich on the stock ECU and they were getting high RPM cut outs. So that sounds promising.

Thanks for your help. I'll post back after some more tinkering.

Cam

[cammmy]

EDIT: This was a post about overlap but I don' t think I got it correct. Going to try and find out what it is tomorrow

[cammmy]

Found some really detailed cam info. It turns out I've got 252* cams, not 272* (they were for the high comp, N/A motors)

252 Duration
104 MOP
22 Intake Opens, BTDC
50 Intake Closes, ABDC
50 Exhaust Opens, BBDC
22 Exhaust Closes, ATDC
44 Overlap

Had a number of replies and it seems my vacuum readings are normal.

"0.55 @ 987"

"On my last log with Espritmon I had 0.66 @989rpm hot idle and 1.15 @3500 with 10% throttle in 5th."

For now I'm going to assume I've got a rich misfire; I'll tinker tonight. I'm going to let the dyno operator do the tuning, I just want to make sure I don't have any real issues when it goes there.

Thanks for all the replies, I'll come back when I have more.

[turbo conversion]

N/A cams are not a good choice for a boosted engine as the grinds (overlap-lift-duration) are completely different.

You really need cams ground for turbo application to get all your engines potential.

I am not saying you can't get a running driving car with your cams, but you will be leaving a lot of drive ability and performance on the table.

If possible you need to get a set of cams ground for a turbo engine before you go to the dyno and spend a bunch of money for inferior results.

My first turbo conversion started out with a N/A cam advertised duration and lift were 270 int 280 exh .444 int-exh. 3000-6500 rpm.

With this set up car was driveable with decent performance but I was disappointed overall.

I then had a cam ground for my specific set up and it was literally mind blowing how drive ability and performance were enhanced.

David

[cammmy]

Thanks, I'll just clarify.

The car was turbo from the factory and these are the factory cams. The N/A cars had 272* cams and something like 64* of overlap. The 252* cams and 44* overlap are the factory cams in my turbo motor.

from my understanding, that was the right thing for Lotus to do as turbo motors don't like big duration high overlap cams?