Will not Rev Past 4000rpm - E38 and a manual tranny with no TCM

[CJ7LS]

Edited for new info/tune/log in the posts below.


Hey folks - new to the forum here and need some input and help.

Here is my setup - Jeep CJ7 with a 2007 LY6 motor (from Tilden Motorsports with their harness) - E38 ECM - NV4500 manual transmission - No VSS

Here are my issues:

It will not rev past 4000 rpm (bucks like it is hitting the rev limiter). This happens when in neutral or under load while driving.

I have searched extensively and have found several references for this issue:

https://forum.hptuners.com/showthrea...-past-4000-RPM (which is pretty helpful) and has several responses from the HPtuner folks

and

http://www.masterenginetuner.com/limp-mode-page-2.html

I have taken the Jeep to Ellis at Speed Secrets in Monroe Washington (who seems well regarded) and he has tried several tune changes to fix this including using the settings described in the other threads (Fuel Cutoff DFCO settings/torque management settings/P/N rev limiter/gear rev limiter etc). This appears to solve the problem for a short time, but it always returns - no rev past 4000 rpm.

Ellis is forwarding me the tune to provide it here.

I have a VSS pulse generator that will work from my mechanical transfercase speedo output. But I have no way to feed that to the TCM'less ECM.

Any thoughts or strategies to fix this would be greatly appreciated. I'm stumped.

Thinking a bit outside the box on this, could I swap ECU's to solve this (as the LY6 in the Yukon never came with a manual transmission). And if so, which one to chose? I'm not opposed to ditching the VVT aspect of the engine (though I'd prefer to avoid that cost of a VVT delete/cam swap if possible).

[Jon S.]

... I have a VSS pulse generator that will work from my mechanical transfercase speedo output. But I have no way to feed that to the TCM'less ECM...

What is the PPM output rate of your VSS generator ?

Why can't you wire it to the E38 ECM ?

[CJ7LS]

What is the PPM output rate of your VSS generator ?

Why can't you wire it to the E38 ECM ?

I've read its possible, I'm just not savvy about how to do it. 128000 ppm sensor from Dakota Digital.

[10_SS]

without a tune or log, not much we can do. Is that drive by wire throttle, if so is the throttle blade closing at 4K?

[CJ7LS]

Agreed, and I?ll get that posted as soon as I get it. And yes, it?s drive by wire with the original pedal. I haven?t checked the throttle blade movement in response to 4K rpm.

[10_SS]

Do you have HPT and the hardware? Make a log showing it and pull the tune. If you dont have the hardware you may want to get it. It's worth it even just to make sure things are running right. And making little changes.

[Jon S.]

I've read its possible, I'm just not savvy about how to do it. 128000 ppm sensor from Dakota Digital.

A 128K PPM system should provide you with excellent VSS resolution. With LSx projects where a useable VSS signal was somehow missed by the owner / build shop, we typically retrofit a Dakota Digital GPS based VSS signal generator (GPS-50-2) - set at 128K PPM resolution.

OK ... you didn’t mention if your wiring harness was purchased from an aftermarket supplier, or is an OEM wiring harness reworked by yourself or someone else - but either way a VSS connection should be in the wiring harness. If your VSS pulse generator has a 2 wire output / connection, then marry these to the VSS High and VSS Low inputs in the wiring harness.

If there is no VSS wiring in your wiring harness, and you are using an E38 ECM, then connect the VSS High signal to the J1 (Black) connector pin 71, and the VSS Low signal to the J1 (Black) connector pin 72. The calibration (tune) will then need to be adjusted to recognize this input signal.

Regarding the throttle closing, this will happen when trying to use an automatic based calibration with a manual transmission. Truck based calibrations require more changes to the calibration (tune) to overcome this issue than car based calibrations.

You are going to need the services of a very good tuner to get you squared away.

[jpierro79]

anything from pick up wire on engine timing to fuel issues can cause your issue. I could hang at 4k meaing you have a a low fuel flow problem to incorrect data for sensors it could bounce like a rev limiter like faulty pick up and cause cel it could be a setting In your rpm section you could have timing multipliers so far off it retards it so far back it wont rev any higher you could have clogged cats if you have them. or goes into failsafe it could think your in neutral trying to launch the car and its not without tune its all speculation so please if you want help from forum people you need to post tune and original tune with your modifications then if we find nothing wrong there first we go to datalogging information to guide you.

There are plenty of knowledgeable people here so please post mods current tune and original mods and we can go from there.

[kevin87turbot]

I've seen this a couple times. Go to Engine>Torque Management>Default Trans Limit. Make sure the it is maxed out above 4000rpm. Most of the automatic cars are populated with negative numbers above 4k.
HPTunersEngineTMDefaultTrans.jpg

[CJ7LS]

Update:

I?ve purchased an MPVI 2 and a small laptop to get the tune and a log. I should have a log up shortly. Thanks for the input folks.

[CJ7LS]

Here is the tune and a short cold start up then rev to 4k limit.

This is my first attempt at using the hardware so bear with me if its not right as far as saving the info and uploading on this forum.

Kevin87turbot has it right I think, as his picture of the issue is exactly the same as mine.

I thought I might post these for others to see if it matches their issues. I'll be buying some credits and fixing those torque management limits shortly.

[x2xplaguex2x]

Well the throttle is definitely not opening all the way. Can you re-log with the car off key on and press the throttle all the way down several times ? Then mash the throttle all the way to the floor with the vehicle running ? Also add ETC Torque Management type to the datapids

[Diggy Moe]

Had something similar.Try lowering the Hot Power enrich TPS table below 20

[S10PARTS4U]

Hmm I just did a swap on envoy and briefly had same issue. Had the Prndl switch bypassed -temporary -and there is a setting for neutral and park for rpm limit, go try raising that to 5350 and see if it changes your top rpm driving... Harness you bought might be hard wired to park/ neutral. Just and idea--

[CJ7LS]

Small update - I'm nearly done with a cam change and valvetrain refresh on this LY6. Once its back together I'll try the changes Kevin mentioned above and delete the VVT on the LY6 E38 tune that is in it. If that doesn't work, then I'll likely flash in a base E38 manual car tune of some sort to start with.IMG_0836.jpg

[CJ7LS]

I got the VVT deleted and the BTR stage 2 cam in. I also edited some fields in the Torque Management section (12836 specifically) that was in the Default torque limit area (as suggested above by Kevin87TurboT - THANKS). All of the values for >3500 rpm were set to negative numbers. I replaced those with 500. Reloaded the tune and the 4000 rpm rev limiter is gone for good.

It also makes sense in this situation where there is no TCM (manual transmission in my swap). Thus it defaults to these limits as it states in the small text at the bottom.

It may also explain why I have somewhat less than ideal power delivery prior to 4000 rpm currently, but once it hits that it pulls super strong. I'm going to go back and set the sub 4000rpm limits to higher and see if that makes a difference.

[Plumber452]

I know this is an old post but I?m fighting the exact same situation. Mine is a 6.0 from an 07 2500 Silverado two wheel drive. My original tuner deleted the VATs, etc. along with the VVT. The car I?ve put it in is an 01 Porsche 911, six speed manual. Car starts, runs great, but....... hit 4K and it?s done. My original tuner has gone MIA so I?ve bought HP Tuners and tried adjusting the settings in Torque Management. No luck. Could you share your tune so I could just load your whole tune and not just changing settings

Thanks

I got the VVT deleted and the BTR stage 2 cam in. I also edited some fields in the Torque Management section (12836 specifically) that was in the Default torque limit area (as suggested above by Kevin87TurboT - THANKS). All of the values for >3500 rpm were set to negative numbers. I replaced those with 500. Reloaded the tune and the 4000 rpm rev limiter is gone for good.

It also makes sense in this situation where there is no TCM (manual transmission in my swap). Thus it defaults to these limits as it states in the small text at the bottom.

It may also explain why I have somewhat less than ideal power delivery prior to 4000 rpm currently, but once it hits that it pulls super strong. I'm going to go back and set the sub 4000rpm limits to higher and see if that makes a difference.

[eboch]

could be the speed VSS isnt reading properly in the E38. The E38 calcs the wrong speed and hits the max-allowed-speed-limiter. I had this problem on an an LS3 swap.

[jELEN]

You need to go into the ecm settings fuel/ cutoff dfco and change the extreme cutoff it will probably set to 4000. im running a e38 with a manual transmission nv4500 with a stock L96 6.0 liter engine and it will rev to 6500 rpm.

[Ansar ali]

Hi sir,
i have a E38 ECM i need tune to tune a rev limiter i am a new tuner please help me sir,