An interesting look at CIS

[randywebb]

If all y'all would eliminate the conclusory statements and personal attacks, this thread would be a lot more enlightening -- let's have more wheat and less chaff from everybody.

[Scooter]

They smoke a lot of marijuana in Sweden don't they?

[beepbeep]

Originally posted by Scooter84
They smoke a lot of marijuana in Sweden don't they?

Wanna see receipt?

German imported 930 -81...worn but fully functional. For price of one SC engine rehaul with extra cheese added.

Yeah, I would also spend 6 months on telling the world how great CIS was if I poured 13k$ into engine rebuild...
Unfortunately, I have other things to do.......

Over & out (now you can discuss that wonderfull torque CIS is developing .... )

[Scooter]

What, did I say something wrong? I had just read the following and posed a simple question:

"Several case reports and one epidemiological study of a large population cohort in SWEDEN have reported that heavy marijuana use for up to one year often precedes the development of schizophrenia. The authors of the Swedish study state that this correlation suggests that heavy marijuana use is a risk factor for the development of schizophrenia.

Other reports, including a study published in the American Journal of Psychiatry, have linked the use of marijuana to exacerbations of psychosis in individuals with schizophrenia. These findings highlight the importance of treating marijuana dependence, especially in individuals with schizophrenia and in individuals at risk for the development of schizophrenia.

Cannabinoids, including THC, are the psychoactive substances found in marijuana. Cannabinoids stimulate cannabinoid receptors in the brain to produce their effects. The hallucinatory and psychotic like symptoms associated with marijuana intoxication have generated an interest in developing cannabinoid receptor antagonists for the treatment of schizophrenia."

[rdane]

Now that turbos and the Swedish dollar discussion out of the way here is some supporting data to Wayne's comments. (what a waste of band with the last page or so has been)

With the A/F ration I am running my car won't gain anything noticable from any engine management for HP or torgue. It will have some little gains in throttle response. After having driven the car..comment is "not much" on throttle response. This from several Motec and Electromotive installers who have reviewed my dyno info. They are telling me my A/F is what they are looking for in their sysytems.

Only small gains with this engine are to be maide by twin plugs...3% by Porsches accounting.

Comparison dynos will be posted before and after that install.

Over and out

[Wayne 962]

Yes, adding an Engine Management System in place of a well-functioning and well-tuned CIS will give you very little gain for your dollar. I'm sure there will be some improvement, as you have integrated spark and fuel mixture, but it will certainly not be that huge (5-10% max would be my guess off hand).

rdane - don't feel bad, you didn't buy a CIS engine, you bought an Andial engine. Standard costs for rebuilds are $8K. Throw in some more $$$ because Andial is one of the best of the best. Then throw in some more $$$ for the 3.2 crank and the pistons, and you can get to that range very easily. You can pop off that CIS anytime you want.

As for discussions about fuel reversion on Motronic engines - beepbeep, you're right. The CIS engine is *much* more susceptible to air vibrations from the common throttle body. You can get good performance out of a Motronic manifold, however, the top dog is the individual throttle boddies like the TWMs, carbs, or MFI.

Engine management is super-ideal for turbo engines, because there's a lot more coordination between the systems (ignition, fuel, boost, and feedback control with o2 and knock) that can be optimized for maximum power. I suggest that anyone modifying a turbo engine seriously consider an engine management system if they are serious about power, control and reliability.

There are really no definitive right or wrong answers here - we all need to play well in this sandbox...

-Wayne

[Wayne 962]

Originally posted by rdane
Now that turbos and the Swedish dollar discussion out of the way here is some supporting data to Wayne's comments. (what a waste of band with the last page or so has been)

With the A/F ration I am running my car won't gain anything noticable from any engine management for HP or torgue. It will have some little gains in throttle response. After having driven the car..comment is "not much" on throttle response. This from several Motec and Electromotive installers who have reviewed my dyno info. They are telling me my A/F is what they are looking for in their sysytems.

Only small gains with this engine are to be maide by twin plugs...3% by Porsches accounting.

The advantage to going with engine management would be incorporating a knock sensor with ignition timing. This will allow you to advance the timing as much as possible without knocking, thus gaining as much power as you can.

Twin-plugging in this case is also not a wise investment. Aside from being very expensive, it's only really practical when you're running very high compression ratios, or running very large pistons (100mm or greater). The beauty of twin-plugging is that it allows you to increase the compression ratio and gain power, while running on the same octane gas...

-Wayne

[dd74]

Ooooo weeee, this is a thread worthy of the OT forum with its...um...spiciness.

CIS - I like it because it's what I have and works for the most part well. But I have concluded that there's no way that I'm going to get the full monty of horsepower out of "gas mileage friendly" injection and pistons. I've read Wayne's book carefully, as well as listened to John and a host of others. The BIG horses come from cubic inches and high comp pistons and any induction other than CIS. But why I'm content with CIS is because it's manageable for me, and my engine seems strong enough with it. This isn't poo-pooing RDane's achievements - not sure I'd go that route in lieu of a 3.2 like Tyson's sorting out, or a 3.6, but still, a 3.4 CIS engine is still interesting.

On the other hand, the $13,500 price tag has always caused a bit of panic in me for what's still a CIS motor. And now with, what, $2,500 more to spend for EFI, well...to each their own.

What this thread has shown me is there's no part-way or half-measure approach to gaining real horsepower out of these motors. You've got to tear down to the bones and build it up much differently. So, does that mean these motors are pretty much the best they can be when they come from the factory? I'd take a chance and say "yes."

YMMV, of course.

[randywebb]

Huh - I always thought it was the plate that made it susceptible to air/fuel mix vibrations... We can all agree that hanging a chunk of metal out there is not the - ah - most elegant means of measuring the quantity of interest, can't we?

THIS BEARS REPEATING:
"What this thread has shown me is there's no part-way or half-measure approach to gaining real horsepower out of these motors. You've got to tear down to the bones and build it up much differently. So, does that mean these motors are pretty much the best they can be when they come from the factory?... Yes"

- Everybody who buys one of these cars and starts looking for cheap & easy Chevy or Ford style hp increases needs to read and reread that. Of course, those people are all on other bbs's -- aren't they?

[rdane]

Originally posted by Wayne at Pelican Parts
Twin-plugging in this case is also not a wise investment. Aside from being very expensive, it's only really practical when you're running very high compression ratios, or running very large pistons (100mm or greater). The beauty of twin-plugging is that it allows you to increase the compression ratio and gain power, while running on the same octane gas...

-Wayne

Sorry to keep dragging you into this Wayne

Guys with a clue on this board (You and Steve Weinier for examples) have always said 98mm and bigger jugs should get twin plugged for detonation. 9.8:1 compression and higher (or 10:1 depending on who is talking) should have twin plugs.

My engine is a 98 Mahle, Max Moritz wedge shaped piston, originally designed to run on 93 octane and single plug at 9.8:1.

Bad tank of gas on a hot day I suspect wouldn't be good for it.
Have you rethought your original comments in the rebuild book and now suggest 100mm as the twin plug threshold with wedge shaped pistons?

I haven't had any problems yet but I would hate to have that infamous "hot day and bad gas" here at sea level and have to do another rebuild.

You can twin plug for less than $1500 plus labor easy enough now.

Would twin plugs be a good investment and a little insurance to keep my 3.4 engine in one piece at that price or waste of money?

[beepbeep]

Originally posted by Wayne at Pelican Parts

As for discussions about fuel reversion on Motronic engines - beepbeep, you're right. The CIS engine is *much* more susceptible to air vibrations from the common throttle body. You can get good performance out of a Motronic manifold, however, the top dog is the individual throttle boddies like the TWMs, carbs, or MFI.

...there is one thing that's bugging me in this approach.

Why should a 930 engine be susceptable for this famed "intake reversion"? All of us that have been fiddling with 930's know that air path between intake ports and CIS-plate (plate that should, according to folklore, shudder in this reversion wake) is laughably long.

There is a intake, intermediate intake, intercooler, a lonh piece of tubing, compressor vanes with extremly tight tolerances spinning at 100000 RPM in wrong direction and then even more tubing in between. Path between intake ports and actual CIS-flapper is probably 1,5 meter long.

There is no theoretical chance that such standing wave could propagate backwards trough intercooler cavity, then compressor vanes and finnaly disturb CIS-flapper.

If there is any reversion happening there, it has nothing with 930 CIS to do. As much as I hate this pesky clog of badly engineered excuse for fuel system, it cannot and shouldn't feel any difference from hotter cams on 930 engine.

My observations on other K-Jet equipped turbocharged engines support this. Check dyno sheet whoose link I posted above. It pictures four dyno runs done with different cam-profiles and adjustments. Last cam choice is very aggressive but CIS happily adjusted anyway, producing 220hp from 2-litre engine (with heaps of boost, of course).

There are lot's of rumours floating around. I never tested different cam profiles on CIS-equipped SC so I cannot comment it, but I'm almost sure that 930 CIS won't feel a thing.


Scooter84: keep driving your Lexus and stay out of tech talk, wouldya?

[Craig 930 RS]

I know both Dane and Randy - local boys, both.

Bottom line ------ Dane, I wouldn't change a damn thing on your engine.
You have a unique configuration 3.4 that works very, very well.

As you and I talked about this afternoon in person, any more changes will cost a HUGE amt of $$$ resulting in very little gains.

Take the money and run........to the body shop for those other smart mods I saw you are doing -

[rdane]

Craig? Surprising dyno, eh?

[Craig 930 RS]

Heck yes. I had to look at this thread after our discussion this afternoon. All the more reason to NOT change your setup!
Hell, if you want to throw away $$$ I'll take em -