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Bad LT
 
Uncle's Avatar
 
Join Date: Dec 2008
Location: Newcastle Australia
Posts: 675
Quote:
Originally Posted by jwasbury View Post
I am happy with CIS. My car runs great.

At the track, I had a guy in the p car modification business tell me "if your CIS is working well, don't mess with it, don't go EFI".

If the day comes when my CIS requires major repairs, I will consider EFI. Until then, CIS is great.

One observation from hanging around this place is that the people who are happiest with EFI seem to be hardcore DiYers. Not to suggest you can't write checks to a tuner to make the mod, you can. Just seems to me that EFI bliss is tied to knowing how to take care of it yourself.
This more or less sums it up for me. If my car came with a good CIS system I prolly would of left it on there. Since I was starting from scratch after selling the Weber's I had on the car the logical path was EFI.

Things I do like about EFI and in my case Haltech. Got a missfire? Plug in Laptop open diagnostics page,right click select new channel,select missed trigger count,sellect missed injector count,click ok. Start car look at screen.
Want less boost in 1st gear and more in every other gear? Plug in laptop sellect AUX driver, select boost control bla bla bla. This is very handy for those with 915 gearboxes lol.

Anyhow just my 2 cents and I clearly fall into the hardcore DIY sub-group

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Ex Porsche Cup car with some boost and stuff.
Old 06-12-2013, 05:14 PM
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Brando
 
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Join Date: May 2006
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Quote:
Originally Posted by Uncle View Post
Want less boost in 1st gear and more in every other gear? Plug in laptop sellect AUX driver, select boost control bla bla bla. This is very handy for those with 915 gearboxes lol.

Anyhow just my 2 cents and I clearly fall into the hardcore DIY sub-group
Hey.......thats an excellent point.
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Turbo powa!
1977 911s. it's cool
Old 06-15-2013, 02:47 PM
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Join Date: Jul 2003
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Quote:
Originally Posted by mark houghton View Post
One of these days the bits and pieces will become unobtanium
CIS would be fine, up to a point, if you can get gas. (Can't say I'm a fan of 8 MPG in town and soggy throttle response, but there you go).

But what about the day when all you can get at the pump is E35?

Leaving politics out of it, it's pretty clear that those decisions aren't based on logic, reason or facts. I think it's going to get worse, before it gets better. If it ever gets better.

The stoichiometric ratio for ethanol is in single-digits, 9:1 instead of 14.7:1 for gas (or twice as much fuel by mass - 11% versus 6.8% for gas). So your chances of getting whatever "12:1 on boost with gas" equates to with (say) E35 - from CIS - are pretty much slim to none right now.

Only reason I can see to retain CIS is on a completely original car, where you hurt re-sale by modifying it - even where those modifications improve the car, make it safer, drive better, more power etc.

Which is why I deliberately bought a bastard - because resale and/or originality concerns me not one jot, and I can fit later factory parts or parts designed in the last 5 years with impunity. Strangely, they often work a lot better than stuff designed 40 years ago - and for a completely different set of criteria...
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'77 S with '78 930 power and a few other things.
Old 06-15-2013, 05:36 PM
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Crotchety Old Bastard
 
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I get 15mpg in town, 21mpg on the highway, and about 8mpg on the track (the one time I went there and took down the data). If you are willing to tune the system it will reward you.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 06-15-2013, 06:25 PM
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I like both but CIS has its limitation. Efi offers a bit more when it comes down to fine tuning your car. If your car is stock or close to it and future value is a huge priority than efi may not be the way to go. I opted for the efi route. Though the future value of my car is a concern, my car was hardly stock. So what the heck, currently she's apart(plus top end rebuild and neccesary items) and awaiting completion. Motec M84 will be my ecu. Power was not my main goal. Linear drivability(or close to it) was the driving factor....plus the fact that my wife told me if I go efi and spend the money, I better keep it for a long time
Old 06-16-2013, 11:59 AM
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Quote:
Originally Posted by JFairman View Post
lol...
I didn't say that I understand 100% of CIS, but with the Leask WUR, a LM-1, and the good old pressure gauges I can get my AFR's good in all the RPM ranges.....doesn't get much simpler than that....

tim
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Old 06-16-2013, 07:10 PM
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Thanks for all the replies. Theres lots of information here and I enjoyed reading every reply. I can say with confidence that I will be sticking with the CIS for now. It sounds like when set up properly, they are indeed reliable

I should probably start a tread on my project but its not a project most of you will be interested in since its not a 930. To be honest, its a bit of a disaster but hopefully fun to drive. Its a 993TT body ( Factory steel panels ) with 993 targa glass roof but based on a 89 torsion bar chassis . . Engine is a 3.3 Turbo, already twin plugged with a G50 transmission.



Quote:
Originally Posted by quattrorunner View Post
I like cis.
It's easy, and works.
If yours doesn't work, fix it.
If you want 500hp then go efi.
Btw I think you'll like the andial Intercooler.
Sometimes we can get freaked out by all the threads about a topic and think your doomed because of them. But reality is less extreme and you just need to sit back and relax.
Build the engine, maybe don't worry about twin plugging as you don't really need it anyway, enjoy that turbo, cis will keep up with it till 1.1 bar at least. You have a better everything.
Build it already and quit making the project more complicated is what I say.
Don't you want to drive it? Hurry up.
Very motivating reply, right to the point. Thanks.
I never dismantled the engine , I did a leak down test when I got it and it ranged from 2-4% . It should be in good condition.
From reading your treads, it sounds like you definitely have your CIS tuned correctly. Thank you
Old 06-17-2013, 06:55 PM
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Brando
 
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Quote:
Originally Posted by herman maire View Post
Thanks for all the replies. Theres lots of information here and I enjoyed reading every reply. I can say with confidence that I will be sticking with the CIS for now. It sounds like when set up properly, they are indeed reliable

I should probably start a tread on my project but its not a project most of you will be interested in since its not a 930. To be honest, its a bit of a disaster but hopefully fun to drive. Its a 993TT body ( Factory steel panels ) with 993 targa glass roof but based on a 89 torsion bar chassis . . Engine is a 3.3 Turbo, already twin plugged with a G50 transmission.





Very motivating reply, right to the point. Thanks.
I never dismantled the engine , I did a leak down test when I got it and it ranged from 2-4% . It should be in good condition.
From reading your treads, it sounds like you definitely have your CIS tuned correctly. Thank you
Thanks.
My cis is not perfectly tuned. I have a few minor issues with my afr on cruise, not too bad though but its spot in with full boost. So it's safe.
I just had a really fun road trip yesterday where I was able to drive without worry about anything. It's dead reliable.
If you buy and use a good afr (air fuel ratio)gauge, it's really easy to adjust the mix.
The good thing is we're always at arm length away to help.
Have fun with it.
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Turbo powa!
1977 911s. it's cool
Old 06-17-2013, 07:16 PM
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Location: Weehawken, NJ
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Quote:
Originally Posted by spuggy View Post
CIS would be fine, up to a point, if you can get gas. (Can't say I'm a fan of 8 MPG in town and soggy throttle response, but there you go).

But what about the day when all you can get at the pump is E35?
I have seen 20+ mpg highway, and generally average in the teens with my CIS equipped 930. 8mpg? Sure...on the track. Whether you have CIS or EFI, you still have to make sure it's tuned correctly. The one EFI 930 I have driven was a major disappointment. It obviously was not tuned correctly. My CIS car blew it away in terms of responsiveness and driveability. So much, that the owner of the EFI car told me after we swapped cars for a spell "I want my car to run like yours". His wasn't a complete mess...idled well, started well, etc. just did not have "it"

Moral of the story, just because you have EFI doesn't immediately mean your car is going to run well.

As to future proofing against E35...it may happen, but there will be a lot more to worry about than our 930s

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Current: 1983 911 GT4 Race Car / 1999 Spec Miata / 2000 MB SL500 / 1998 MB E300TD / 1998 BMW R1100RT / 2016 KTM Duke 690
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Old 06-18-2013, 03:21 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #29 (permalink)
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