Juha G

I do know that the eaton blower makes loud whining noise. However it Will blend in nicely with the whine from my straight cut gears and exhaust note...

haygeebaby

Nice project Juha
Looks like my winter all over agin. But will be interested to see what figures you get with the addition of the Motec unit.

Juha G

Motec with bigger injectors is of course a much better way to adapt to the additional air flow from the SC than some piggyback system with additional injectors. Much more accurate so at least I should be able to make the car very driveable.

I couldn't keep my hands of the car and went to the garage this morning (it is Finnish independence day today btw!! ) and took out the seats, roll bar, 6-point harness and some interior bits.

God damn, they are diiirty!!


Moton reservoir has to go (for now)


It's a big mess at the moment. I am thinking if I should have the center console clad in black alcantara or leave it out, RS style


The rear doesn't look too good either. A little levelling out and then RS carpets in.


I'm wondering if I should have the rear side panels upholstered in black alcantara and keep them together with the RS carpets. Should look nice!?
And for the rear shelf I think I will make a very thin plywood sheet that I will install the RS carpet on. I don't like how the RS carpet looks over all those bumps there...


The roll bar is going to get powder coated in silver. I'm pondering if it would look nice with the seat backs in silver as well???


I have a new cover for the driver's seat. The old one is in horrible shape...


The belts are off and sunk in bath... =)



Next is wheels, brakes, suspension and rear bumber. Stay tuned!!

Marc Shaw

According to Geoffery of RaceTech Engineering (who posts on the 964 forum) and Red Rooster/Geoff of AMD (now deceased), the additional injectors are actually more for cooling intake air than trying to atomize additional fuel.

IIRC from Geoffery's posts, the only engine he ever detonated was trying to MOTEC tune a TPC SC engine without the extra injectors.

If you leave out the extra injectors, at least put in an IAT sensor so you don't get temps too high and develop pre-detonation or detonation issues.

Marc

Juha G

Marc, it is not that straight forward.
With the SC you are throwing in a lot more air (oxygen) and if you do not add any fuel, the engine will run lean and you will end up burning holes in your pistons...

The stock Motronic unit is basing the amount of fuel injected on the pre-made mapping (rpm vs. MAF). On partial throttle it also does a so called lambda correction, aiming on a stoich a/f ratio. At WOT there is no lambda correction and the amount of fuel injected is based solely on the fixed mapping. When you start adding more air to the mixture (with the SC) at some point you run out of the map (MAF reads higher than values on the x-axis), which means that you wil not get more fuel and results in a lean mixture...
Even if the mapping was done 50% beyond what can be achieved by a stock engine, you'd quickly end up maxing out the stock injectors capacity.

It is true that the additional fuel has some cooling effect but that is not the reason the additional injectors are there. The real reason is to achieve right mixture of fuel/air.

The water/methanol mixture also has a better cooling effect than fuel.

Detonation is a real concern but when the mapping is done right, it is not really a problem at all...

Marc Shaw

Obviously more fuel is needed but my point is that it helps more with cooling than you may realize but a Snow or Aquamist system would help too (more alcohol and water than just water though).

"The issue with the Eaton supercharger is one of intake air temps. The 7th injector is used more for cooling the intake air charge (and surrounding metal) than for fueling, although it helps with fueling. Without the 7th injector, I could not get the intake air temps to a reasonable level and at one point detonated the engine and broke the compression rings due to the excessive heat and ignition timing that had not been compensated enough for higher intake air temps." - Geoffery

Regardless, I look forwards to you progress.

Marc

Juha G

I don't think it makes any difference whether you inject the fuel trough 6 bigger injectors or 7-8 smaller injetors. I guess the point here is that more fuel is needed than you would need just for an optimal a/f ratio!?
The richer the mixture the lower the temperatures.

I think I should heed your advice about the IAT sensor. On my supercharged M3 I had a EGT sensor, which also tells you if you are running too lean.

Detonation is also very sensitive to ignition advance. You can very easily destroy your engine with too much advance, especially on a high CR engine like the 993 engine...

Thanks for the comments, it will pay off to be thorough with this.

And who knows, I might end up adding an IC later on...

axl911

How are you using EGT to tell you're running too lean? I have an EGT, but never really look at it since I also have a wideband O2 sensor for AFR.

trophy

Juha, you have an IAT already in your car, for an 88pin Motronic it uses Pin 47. (For 55 pin Motronic it is also pin 47).

Connect it up to a temp or aux input on the Motec and you can use it to track IAT as well as use it as a parameter for timing (gets too hot and retard ignition etc) can also be used to help with cold start and cold idle in the frigid north.

trophy

Here is some good info on EGT vs AFR...

http://www.sdsefi.com/techegt.htm

NineMeister

Volumetric efficiency, compression ratio, spark plugs, fuel mixture, exhaust gas temperature, cylinder head temperature and air temperature are just some of variables in the highly complicated equation of combustion. Even though most tuners measure lambda, EGT, IAT, & ET I honestly doubt that any of them can actually know what is really happening in the chaotic burn space of the piston/cylinder/head assembly, however the better ones will have a feel for what is acceptable and be able to tune the engine according to their understanding and experience.

Lambda and exhaust gas temperature will not tell you what is happening in the cylinder - it tells you what is happening in the exhaust pipe. The two are not one and the same. On a supercharged engine with the likelyhood of blow-through on overlap and with a rich mixture to keep everything happy the engine will probably have poor combustion efficiency (lower mass fraction burn) resulting in the wasted fuel burning in the exhaust port. It will be the combination of cylinder, port and pipe combustion that the sensors measure, so as you are only interested in is what is happening in the cylinder, you must make allowances with the numbers you read 800mm down the pipe.

I'm not saying any more other than this: The fact is that the 7th injector is definitely a compromise in terms of fuel distribution but its location provides an important (maybe critical) secondary function of cooling the intake charge in the manifold. I've tuned 964 supercharged engines on Motec without a 7th injector as has Geoffrey and we've both been caught out with unexpected detonation resulting in a broken piston ring. We learned this the hard way and we've told people about it on Rennlist so that they don't make the same mistake doing a similar job, so if the advice of two reasonably experienced Porsche engine tuners is to be careful with intake temperatures on your supercharged engine, I would take the advice seriously and consider it reasonably important.

Juha G

Thanks for the advice Colin. I would assume the water/alcohol injection has the same (or actually better) cooling effect as the 7th injector. Do you agree with that?
Running the IAT input into the Motec, we should be able make the system fail-safe (i.e. when IAT rises above a limit, motec retards ignition), just as suggested by Trophy.
Do you think we can make it work like that or do I really need that 7th injector?

The tuner has 25+ years of experience building and tuning racing engines (for rally and road racing). So if the system works in theory, he will make it work in practise too.

I appreciate all the help and comments. Isn't this a great place!?


Edit: I called my tuner and checked this; the Motec already retards timing based on intake and engine temperature. So the fail safe system is already in place. He also agreed with you that placing a 7th injector further away from the cylinders will have a cooling effect but better results can be achieved with the water/methanol injection.
He did recommend getting a intercooler, which I am thinking about now...

NineMeister

His advise is good. You should forget about water/meths injection and fit the intercooler, I would hate to think that you could kill an aircooled engine by running out of water!

Mike J

evoderby

Science at least agrees with that;-)

http://autospeed.com/cms/A_110213/article.html

When done right, water injection is a very very very effective means of surpressing detonation. Much more so than adding fuel!

However, running out of water without any warning or electric pumps getting stuck are a smart way of blowing your engine in seconds. Make sure you use the best....