NineMeister

Here's something a bit different that I thought you all might enjoy: it's a 911SC that has been rebodied as a 911ST and fitted with a stock 964 engine; in other words it's a typical R-Gruppe car that is used for weekend fun and trackdays.

The customer has been in discussion with me for a few months before finally taking the plunge to drop the car off for phase one which is a fairly straightforward 9m Motec conversion. At some later stage in phase two we will be fitting a set of 9m ITB's to give it the correct retro look to the engine bay to match the exterior. Apparently the car was built in Europe and we were told that the ecu has been "remapped" to suit the SSI exhaust which is currently fitted.

As part of most 9m conversions the first thing we do is put the car on the dyno to find out what we are starting with, so with the engine duly warmed up this is what we found after three dyno pulls. Note that we now have on-dyno lambda logging, in this instance it made for very interesting reading.

NineMeister

OK, so it's fairly obvious to most that the so called remap was not too successful in achieving a flat line optimal mixture, so I guess that this needs to be kept in mind for the gains we will find with the 9m Motec package.

The more interesting point to note for me is that looking at the dyno result the engine did not produce the expected lump of midrange torque from the 964 resonance flap intake system which (in my opinion) should be further boosted by the SSI exhaust. A quick investigation under the engine lid revealed that the resonance flap actuator was disconnected and had been replaced with a spring to hold the flap permanently open, hence the strong top end and poor midrange. So, I have a bit more work to do whilst the throttle body is modified, but in the end I expect to see pretty strong gains across the board on the Motec is fitted.

Auto_Werks 3.6

Colin,

Just shooting from the hip here regarding the air fuel. I'm curious if that could be a mechanical problem with the the air velocity meter. The lean and rich spike correspond with maxtorque (VE Max), so I wonder it the meter hangs a little, and then springs too far open with momentum once it moves again. I see it is also mounted at an angle, which may compound the problem....Or, the map is just garbage, but it would be interesting to know what causes that little hiccup.

NineMeister

That's a fair point Ryan. To be honest I had not given it any thought other than seeing that it was not ideal, but now that you have mentioned it I agree that this is a possibility. In normal circumstances the geek in me would take over and I would run the car up to investigate the cause, but in this instance given that the resonance flap is not even connected there are bigger fish to fry. In any case since the customer is only paying me to fit the Motec (& hopefully to rectify the res flap fault) I'll have to pass on this interesting diversion for now. Good call though.

Auto_Werks 3.6

I don't blame you for not investigating... Even if I weren't on the clock it would be hard to justify spending much time on parts that are going to end up in the bin. I'm sure that car will seem loads faster with some more mid range. My personal car really only makes any torque from 4500 to 7500 RPM, and its hard to maximize area under the curve without short gears. What do you expect to net from it with the modified throttle body / MOTEC conversion?

On a side note, I'll be attending EFI university's 101 & advanced classes in Ohio in the next few weeks. I don't know if anyone from our community, or any of your 9m USA contacts will be there. Do you know of anyone I should keep my eyes open for?

NineMeister

3000rpm is not a bad rpm range to have since with stock gearing the maximum rpm drop is going to be 1st to 2nd where you will lose 2500rpm. The downside is when your corner exit point is between two gears and you are maxed out in one and under the torque peak in the other, which is where a close ratio gearset comes in handy. In contrast, I'm expecting this engine to produce around 380Nm at 4500 and eclipse 310bhp at a 6000rpm peak (flywheel corrected) with the Motec package, so that's 10% more power and 15% more torque according to our dyno. Let's see, eh?

I'm not sure if Geoffrey will be there, but either way the boys at EFI know their stuff and I am sure you will get an awful lot from the course. Be sure to post a thread with a report on how you got on.

NineMeister

As a result of the resonance flap problem I removed the intake manifold today to effect a repair on the flap actuator, however I was not expecting the find the second issue of a broken resonance flap. I've now replaced the centre section with a part from a spare 993 manifold and have also taken the time to clean up the residual oil out of the plenums. Some oil in the manifold is normal, however this looks slightly excessive so I will have to look into this as well once the engine is back up and running.

Just goes to show that there is never a "straightforward" Motec conversion and also how important it is to check everything as you go, otherwise the customer could have been paying twice to remove the intake manifold & take it apart.

crg53

Colin, I have always been under the impression that the SSI exhaust was too small for the 3.6L engine i.e. 1 5/8" pipes not capable of handling the volume, but on your dyno result the max HP for a stock engine is very good, care to elaborate.
Keep the stuff coming; last night I was trying find a picture of an old Lambretta I used to own, it was called something like a "Parashute Model" IIRC, maybe late 40ish-early 50ish, front fairing barely reached the knees and no cover on the engine, 3 speed tranny operated from the left handle.

Thanks

vanhauen

As part of the S/T conversation done a few years back I was keen to retain an ability for heating during the cold winter months in northern Europe. The resulting SSI system was sourced from Patrick Motorsports who have had these specifically designed for 964/993 engines, i.e. the thick head flange type used has a tapered inlet port for the 3.6L head. For more details, have a look at their site: http://www.patrickmotorsports.com/part/186/

NineMeister

Over the years I think I have made a fairly strong case for small intake ports with high gas velocities, so when it comes to the exhaust to a degree the same rules apply. Small exhaust primary pipes will "hold back" the exhaust flow from EVO (exhaust valve open) to BDC (bottom dead centre) hence retaining a higher pressure in the cylinder which makes more power during blowdown. Once the gas is up to speed, the higher velocity will then reduce the gas pressure in the exhaust port at overlap (both valves open, inlet opening + exhaust closing) which thus improved cylinder scavenging. When all this is happening, the engine makes more torque.

The trade-off comes at high rpm when the gas flow increases to the point that the flow "chokes" in the primary pipe, at which point the cylinder will not have enough time to clear the exhaust gas and the torque will then reduce. The rpm when this occurs is largely down to the specifics of the engine design, i.e. capacty & state of tune.

My guess is that the SSI's will work well on a stock or mildly tuned 3.6 since the header pipe diameter is not too dissimilar to that of a stock 993 heat exchanger, so for me they are a good choice if you also consider that they will have a fantastic heat output, however you may want to consider other options for a 3.8 litre race engine.

Glad to know there are other Scooter enthusiasts out there. Keep following the 9m Vespa thread, not only have I just bought a 125GT for me and the wife (she knows now) but Marc is considering buying one for him & her as well, in fact I couldn't get them off mine the other night when we had it running!

Bill Verburg

I dynoed my stock 964 w/ ssi's which incidentally have 1 3/8"(35mm) ID primaries and later w/ B&B w/ 1 5/8"(41.9mm) ID primaries, the difference was ~15hp at 6400rpm. around town the ssi's were fine but at full rpm the engine was strangled.

stock 993 pipes are 38mm ID
stock 964 though its a mess otherwise uses 41.3mm primaries
993 Cups used 42mm ID primaries

DaveConn

Sorry in advance for the hijack, guys (but seeing as the discussion is appropriate)...

Colin, I sent you a PM a couple of days ago regarding headers for a mildly tuned 964. Did the PM come through on your end?

Thanks in advance.

Regards all,

Dave

crg53

Thanks Colin, that answers my question. Looking forward to see the dyno results for 911SC with 964 engine on Motec; are the SSI's staying on the car or are they changing to something else.

Bill, it is my understanding that SSI makes 1 5/8" primary's, maybe I am wrong, will look into it as I really like those exchangers.

Bill Verburg

SSI only makes 1 1/2"OD/1 3/8"ID primary pipe systems

Auto_Werks 3.6

Colin, I said I would report back after the class... You were right, the 101 and advanced classes make for quite an experience. After day two, I went home and made a fuel map from scratch that operates 100 times better than the "professional" tune ever did. I have not had a chance to do much road testing, but as far as I'm concerned I got my money's worth before we even hit the dyno portion for day three! I can't even begin to identify the mistakes that were made when my engine was calibrated initally, the company made mistakes at almost every opportunity. I probably should do a more in depth write up, but I'm not ecactly sure what board to post it on...

How is your project progressing?