964 Tuning issues - new FVD cams and M1 MOTEC ECU

[NigelJones]

Dear all

Summary of the issue

I have new cams and ECU on my 964 engine. I am disappointed with the result but I am not sure if it is my expectations that are at fault or if the tuning is off (or something more serious needs attention). I am hoping for some feedback and guidance on next steps.

Background

I have a lightweight longnose with a 964 engine and a G50 5-speed. Until recently, this was running an Autronic ECU set up that I was never very pleased with. The car did not run that badly, but the tuning was just a little lumpy and, despite a revisit to the Autronic tuner, it was starting to burn the plugs. I didn’t have much confidence in the Autronic tuner (I think the tuner was more the root cause of the poor tuning than the ECU).

My workshop and the MOTEC tuner built another 911 for me that has been a great success. Regarding this car, they recommended switching ECU systems and the proposal was to upgrade the cam at the same time to get a little more out of the engine. They recommended the very latest M1 MOTEC ECU that has dual lambda and anti-knock and the advice was that this would give complete control over the engine. For the cam, an FVD Club Sport (300°-300°-112°) was chosen. The car is not a daily driver and is used for brisk Sunday morning driving. I am after something with low down torque rather than a high powered race car.

This set up appears to be the cause of my current problems

Engine set up

The 964 engine set up is as follows:

- rebuilt only 25,000 km ago. It has not had a hard life
- 3.8l
- twin plug
- it was running a slightly upgraded cam
- quality aftermarket headers + Dansk exhaust with a single outlet made for the 964 in a backdated car

Latest work

To swap the cams and ECU the following was done:

- new Clewett trigger wheel
- new distributor caps
- new plugs, oil change etc etc
- new FVD Club Sport cams 300°-300°-112°
- new M1 MOTEC ECU + new part wiring loom
- new Bosch lambda sensors plus the anti-knock bridge

Symptoms

The engine is very stable and therefore not what I had imagined for a ‘Club Sport’ cam. The G50-rattle in the gearbox (from shortening the bellhousing) has gone. That surprised me but the workshop explained it as being a result of the improved engine management control. Also, turning the aircon off and on has no impact on idle or the tone of the engine, quite different from before.

The workshop and tuner tell me that the car is good and finished but I have three issues:

1. vibration or hum: I cannot describe this very well, but there is a hum, or a buzz or resonance this is just not comfortable. At first I thought that somehow the engine was touching the bodywork and that it might be running on 5 cylinders but we cannot find anything. The old smooth sound has gone and there is now more of a low frequency hum.
2. Engine heat: the car is running noticeably hotter. Previously, the engine was very cool to the point where the service guy would jokingly complain that it took a long time to warm up. Now the workshop is telling me that I am going to need to add in another fender radiator.
3. No longer free revving: the engine has completely lost its free revving character. In neutral, if I blip the throttle the revs are slow to climb. If I hold the revs at, say, 3,500 and lift my foot off it takes a couple of seconds for the revs to fall back to idle. Changing between gears is weird, there is no need to toe-and-heel to match revs as the revs hardly fall at all!

To top it all, the engine feels no more lively than before.

Questions / feedback please

Q1. I am ignorant of what a ‘Club Sport’ cam with that much overlap should feel like? I had expected a lopey cam and a temperamental car at idle, but I seem to have the opposite! Is the buzz consistent with this kind of cam?
Q2. Does the change in cam really result in a meaningful increase in heat to warrant an additional fender radiator?
Q3. What is up with the lack of responsive engine? I am utterly convinced this is not correct.

Next steps

Subject to the feedback, I am thinking that the next step is to go to the tuner (the workshop has now put me in direct contact). I think that this is a new ECU with no engine maps and fear that everyone is trying to figure out how to use this. I am a bit surprised that the tuner did not supply me with a dyno print out, this seems pretty essential to know whether the engine is performing correctly. Subject to how much progress I can make, I am wondering if I can get some support from MOTEC?
Worst case, if your collective advice is that this is correct for a Club Sport cam, I could consider reusing the old cams but then the debate will be whether the tuner can convert his existing 964 maps onto the new generation of M1 ECUs.

I hoping the collective wisdom of Pelican and guide me on how to handle the analysis.

Thanks

Nigel

[Raceboy]

First question, why the need for Clewett trigger if 964 engine already has the best possible trigger from factory, a 60-2 on the flywheel?

Autronic is a very good system and I find it difficult to prefer Motec M1 over any Autronic capable of running 964 engine...

Did your car ever visited a dyno?? Hot running indicates totally wrong timing advance, air cooled engines are sensitive to that..

I would recommend changing your ECU to VEMS plug and play system I am offering but I realise that this would be just a bad joke to you after all the frustration..

[NigelJones]

Raceboy - thanks for the feedback and recommendation for your VEMS system. The Clewett trigger was added because the prior Autronic system used a different trigger. Whilst the engine is a 964, is it in a longhood and so the G50 bellhousing was trimmed to get it into the car (and along the way does not have the standard flywheel). As mentioned, the tuner did not share the dyno output which surprised me. I am thinking that this would be the next steps to try and diagnose the problems. You have guided that the engine probably has the wrong timing advance (which certainly confirms my guess that the mapping is totally off) but do you have any guidance on whether totally wrong timing advance would result in such a lack of response to the engine?

Does anyone else have expereience of an FVD Club Sport cam and be able to guide me on the 'feel' of that cam?

Many thanks,

[SoyRacer]

The biggest problem I've had in the past with 964 crank pulley trigger wheels is getting a true tdc. I had one off by almost 4 deg and difficult to verify with engine in the car. Ended up utilizing a Carrera cup-car clutch with the Cup flywheel to use the factory crank sensor pickup.

Good luck

[Jeff Alton]

Did they provide the cam specs? " club sport cam" sounds pretty mild, but need the specs... what intake system in on the car? Stock 964 or ITBs?

Cheers

[robcf]

Simply changing parts in and out wont resolve your problems. As you identified, go speak with the tuner about your concerns, have them drive the car so that you both understand the issues.

I would not be satisfied not receiving a dyno print out. However, the printout will only indicate the peak engine performance, it will not describe the dynamic performance.

The M1 ECU is much more developed than the Autroic ECU, not surprising considering that the Autronic SM4 have been around for some time. The M1 ECU uses a modern VE fuel model which should offer superior engine calibration as it is much more capable of metering fuel over a wider range of conditions (environmental and engine) with greater precision.

Bottom line go speak with tuner.

[NigelJones]

Soyracer - thanks for sharing the experience with your crank pulley trigger. Definitely an issue worth keeping in mind as a possible cause of the problem. At this stage, I am trying to establish whether my experience is at fault (ie is this normal for such a cam), is the tuner at fault (not familiar with the new ECU) or is there another mechanical issue (such as a trigger that is off).

Jeff - the cam has a reasonably long overlap - 300°-300°-112° - and described as 'club sport race', so yes I had expected it to be a little more lively but not unpleasnt to use. Here is the link to FVD, but regrettably there is less detail than is ideal.

FVD Online Shop - 100105274 - Camshaft "3mm" 964/993 (left) club-sport race, 3,00mm -

[Tippy]

It's all in the tune! Just needs more tuning, and you'll be happy.

[NigelJones]

Tippy - thanks, appreciate your encouragement. Feeling pretty unhappy now so seeking guidance from you knowledgeable folks. As I say, I cannot believe that just swapping a cam is going to require a whole new oil cooler.

[Tippy]

Timing is too retarded. My car ran a lot hotter moving timing from 15 to 8 degrees at idle. Took it to 10 degrees, and found a happy median between smooth idle and engine temps.

I'd just express concerns with tuner.

[Raceboy]

Originally Posted by SoyRacer

The biggest problem I've had in the past with 964 crank pulley trigger wheels is getting a true tdc. I had one off by almost 4 deg and difficult to verify with engine in the car. Ended up utilizing a Carrera cup-car clutch with the Cup flywheel to use the factory crank sensor pickup.

Good luck

This would be my first thing to do: verify missing tooth position relative to TDC with a strobe light. If that checks out, cam timing would be my next target together with compression tests.

ECU manufacturer doesn't matter if the tune is bad, especially on the engine as simple as 964.

[Tippy]

^ yep! Carbs can run better than the most expensive MoTec if the tune is bad!!!

[NigelJones]

Dear all,

I wanted to report back on the solution for this tuning issue. I would like to make sure that anyone reading this in the future can learn from our problems.

Having questioned a couple of times whether the timing was too retarded, I eventually asked the workshop to reverse the cams back to the standard cams that I have been using before.

As they were getting ready to start the work, they made one final check of the timing and decided to get a new timing gun (just to be sure). The timing was running 20 deg off! I guess it is a credit to the new MOTEC system that it could even start up.

Suffice to say that the car is back. Here is a dyno run (the numbers are at the wheel, using a bolt on hub). The relatively flat torque curve is very encouraging. There are one or two quirks around 2,700 rpm to be ironed out but it sure runs better when the timing is right.



Nigel Jones

[Raceboy]

Glad to hear that it is working properly now and I am glad that the symptoms pointed to right cause (wrong timing).

[Tippy]

Nigel, you are probably like me, envision the worst when it's something simple.

Glad I was right (retarded timing), rewiring or changing parts in a shotgun approach is draining and frustrating.