3.6 - 3.8 Upgrade - Ignition changes needed? Any experiences/suggestions?

[katigbr]

I'm currently planning to upgrade my 3.6 to 3.8 this winter and have heard conflicting advice regarding required changes to the ignition system. I'd like to get some idea on what the potential issues are before I'm stuck with a big $$ surprise later on.

My plans are to modify the engine for more higher end horsepower using a pair of GE-80 cams as the basis. Apparently, the Motronic system will not operate with cams of this nature. Aftermarket engine management systems are outside of my budgetary limits and in order to save some cash, I plan on using a set of 50mm PMOs. I was hoping to use the ignition circuit on the Motronic DME but am not sure if it can work independently of the fuel management system. Will I be able to use the current Motronic system for the ignition control or will it be rendered inoperable by the lack of input from the various sensors on the intake side (MAF, TPS, etc). Anyone been there done that?

Additionally, anyone have any recent experience with aftermarket engine management systems. Motec is too expensive and there is limited documentation on what the alternatives are. Anyone want to share their experience/recommendations? It seems that the biggest issue with EMS are the dollars required to tune the systems. Everyone seems to agree that they will make horsepower.

The plan is to upgrade the valvetrain with racing springs, Ti retainers, upgraded valve guides and mild porting/polishing. I will be using either new Mahle P&Cs or rebored Cylinders with JE pistons and Pauter connecting rods.

Thanks,
Rick

[widebody911]

There's a guy here locally with a 3.8L track car, and I believe he's running Haltec. If you wish, I could hunt down his email address.

[katigbr]

Thom,
If you don't mind that would be great. I'm flying blind at the moment and welcome any info I can get.

Rick

ps. I hope you don't mind but you inspired me to build my own (SPI) Sewer Pipe Intake from pics of your own development effort. There was a decrease in initial throttle response but seemed to have more top-end power (comparative butt-dyno sampling). What were your observations?

[Bill Verburg]

Rick, its not the ignition, it's the fuel meter used w/ either 964 or 993 thats incompatible w/ long duration cams like the GE 80. The lumpiest you can use w/ Motronic in the Webcam 20/21. If you go w/ the carbs you will lose some of the teriffic flexibility of the Motronic engines but gain some great power at the top. Are you building a race only motor? If not stick w/ the milder cams and Motronic.

Sounds like we have similar projects going. I've got some 102mm RSR p/c going into a 97 variram, but will stick w/ 993RS or 993ss cams. Streetcar you know

The piston on the left is one of the PMS 102 RSRs, note the coatings and tapered wristpins, very trick

[CamB]

I have absolutely no idea how the Motronic works and whether it could be "tricked" into continuing to supply ignition only.

My experience with MoTeC is that is just keeps adding up. The actual computer was only about US$800 (second hand older model) but the sensors (you have many of these) and the tuning (and the bigger injectors which you will need) all add up.

It would need about 1/2 - 1 day on the dyno if you went EFI. You should get 340-350hp on pump gas (my engine builder has almost the exact configuration - a 964 engine with 3.8 Mahle kit, 11:1 ish c/r, 50mm throttle bodies, 944T injectors, older MoTeC and GE80 cams. From my other discussion on dyno correction, I better restate this as about 315 rwhp. You can apply any correction factor you like!!!

Now as to just mapping ignition. I would imagine it would still need some time on the dyno (just not as much). Given the cost of PMO 50s, you should at least check how much EFI manifolds and a fuel rail is. I bet it adds up like you wouldn't believe.

There are so many companies making EFI - off the top of my head:

http://www.turbofast.com.au/autronic/autronic.html (ex-MoTeC people - apparently better and cheaper)

www.haltech.com.au

www.motec.com.au

www.sdsefi.com

www.electromotive-inc.com (they have ignition only option in conjunction with crankfire conversion)

There are a few in the UK too (eg search for "Emerald" and "Alpha") and I'm sure there is something in the US.

I would be inclined to fully map the ignition rather than the simple electromotive option (but hey, it isn't my money!).

[Bill Verburg]

I just noticed that I never addressed your main question. Yes, its fairly common to separate the ignition function from the FI function for use w/ carbs. You would want to talk to Steve Weiner for details.

If you are building a race car I can put you in touch w/ a fellow relatively near by that has 2, 3.8 RSRs w/ the PMS version of Motec. $24k or $30k take your choice. They are not streetable nor will they run on pump gas. I also know of a fellow w/ a 3.8 RS ~$19k and a somewhat more reasonable 964 3.8.

[katigbr]

CamB,
Thanks for the leads on the EFI providers. There are a lot of them to consider. I'm currently talking to SDI. They are based in Canada and have a simplified programming process. I'm still educating myself on what my needs are but am intrigued by their offering. Everyone still feels MoTeC is the ultimate but as you pointed out, the costs do add up. I priced a set of TWM throttle bodies, fuel rail, injectors, etc. and was quoted $4400 for the package.
Other than the current injectors, shouldn't I be able to use my current induction system? I'm assuming that there would be significant throttle response improvements and perhaps higher peak HP by going to the individual throttle bodies. I believe the the 3.8 RSR had an individual high-butterfly setup for this reason.

Bill,
I'm beginning to look around for an exisiting 3.8 as an alternative. I'm learning that the 3.8 upgrade is probably 2-3 times more complicated than the 3.6 engine swap. The mechanical process is fairly straightforward. It is the ignition and fuel management system options that are the most intimidating. Steve W. and I have been working together on assembling the 3.8 upgrade components but I had not really finalized the intake/ignition setup. PMOs are the cheaper solution but I'm thinking that if I've got to shell out money for an aftermarket ignition control system or remapping the DME then I might as well look at going full EMS. The high cost of the TWM induction setup has me worried about the feasibility of this option. Your suggestion of milder cams may be the smart way to go. What kind of power curver and peak HP are you expecting? My car is primarily a track car with some limited (2-5%) street use.

Rick

[CamB]

Well, here is the world how I understand it (remember I don't do this for a job so take it with a grain of salt)...

"Other than the current injectors, shouldn't I be able to use my current induction system? I'm assuming that there would be significant throttle response improvements and perhaps higher peak HP by going to the individual throttle bodies. I believe the the 3.8 RSR had an individual high-butterfly setup for this reason. "

Once the camshafts get behond a certain level the ability of airflow devices (eg MAP) to measure fluctuating airflow at low rpms means that the car can't be made to idle.

I would have this same problem (S cams, MFI throttle bodies converted to EFI) but I don't have an airflow sensor. I have only a throttle position sensor (TPS). The EFI has two simple tasks only:

- a fuel map every 250rpm and every 10% of throttle opening
- ditto ignition map

There are a few (very few) other settings and sensors - air temperature, coolant (oil of course) temperature, ambient air pressure. My computer doesn't measure:

- air volume entering engine
- air/fuel ratio
- presence of detonation

It could be considered pretty basic. It is really only a slight flasher version of MFI, in that the ignition is also mapped.

So what does this mean for you (IMO). There is probably no reason you couldn't use the intake you have but modified to use only a TPS. I would talk to the experts about this. You may get away with using your existing injectors - you will just have to crank the fuel pressure way up to make them flow enough (I am conservative so I wouldn't do it). You will probably already have the other sensors and it is just a matter of determining where and how to interface them with the EMS.

With just a TPS and what are reasonably aggressive cams, my car doesn't run perfectly at low revs (1000rpm) but it does run ok. It pulls cleanly from 1500rpm up. Fuel economy is pretty average, but who cares?

[Bill Verburg]

Rick, It sounds as if your goals and mine are quite different. Mine is first and formost a street car. I will not sacrifice tractability for a few hp at the top end that will rarely be used. You are building a racecar that doesn't need the low and mid range torque as much.

Which ever way one goes there are no off the shelf chips, so a custom chip needs to be burned from dyno time. This needn't be exorbotant, its been estimated to be from ~$600-$1200. Another alternative is a Unichip in the same range or just a little more.

For a race car the GE80 w/ PMS carbs is a good setup, it won't match the ultimate gains available from a Motec/TWM setup but it will be less than 1/2 as expensive.

Mine hopefully will be in the low 3s, the true RSs are also in that neighborhood, the RSR w/ Motec or equivalent are in the mid 3s

As I said I found a couple of real 3.8 RSRs that have 350-380hp but they are in no way suitable for street use or pump gas.

Cam, posted some of the other possibilities for other engine management sytems, some look to be as promosing as the Motec for less $. Again dyno time will be essential so you may want to look into tuners/builders w/ acess to a dyno. Here in the east they are not as common as in Ca. But there are a few within a 4-5 yr drive of your location. They tend to be concentrated in the NYC, Boston or other Metro arears but I think that there is one in Burlington Vt. also. Keep us posted of your progress.