EFI intake questions, tbitz questions

[Shuie]

Im investigating EFI for an engine that has carbs right now. Any kind of EFI/engine management I try to go to will require buying an intake among other things. Im a total noob with EFI conversion knowledge.

t-bitz questions
Has anyone adapted the t-bitz/Megasquirt CIS to EFI conversion to work with a Carrera intake manifold? Would there be any benefit to using the Carrera manifold instead of the CIS manifold?

Has anyone done a before and after dyno yet with the tbitz conversion? Noah, how is your car working out so far?

MFI intake?
What about MFI stacks and throttle bodies? Has anyone ever used them for an EFI conversion. Would these flow better than both the CIS and Carrera intake?

TIA

[67nin11]

i was wondering about the carrera intake myself. fabbing the fuel supply for my cis setup was time consuming (still not done with the tank/fuel pump) .
i THINK you could use all the carrera plumbing , BET that it flows better and KNOW it looks better. you would have a much more modern engine when you were done.
my question would be if the bolt pattern/spacing is the same for the early engines?

[dean]

The bolt pattern is the same. You have to change the studs. The port size is bigger so you should do something to make it match better
Dean

[Alan Cottrill]

the carrera intake vs. MFI/individual tb's is dependent on the cam your running.

is the motor in your T stock?

if you want to run a cam designed for carbs you best bet is individual tb's. Either modify some MFI tb's or buy some of the commercially available EFI tb's such as TWM's. If you try to run a cam with lots of overlap with a common plenum manifold of any type you will have problems with air reversion into the plenum which will result in low manifold vacuum. a guy over on the megasquirt board was running cams similar to "S" cams and decided what the heck...lets try a carrera intake and see what happens. his car would barely Idle and his idle map was somewhere around 80Kpa (ambient Kpa at my elevation is 94Kpa) I'd guess a lobe angle any narrower than 108' would give you problems with a common plenum.

so, as far as which would flow better, I think either one would flow fine if it was suited for the type of cam you're using. If you're using a cam designed for CIS, I don't think there would be any real benefit to using individual tb's. if your engine has cams desingned for use with carbs you will have trouble using a common plenum intake.

so as with most things relating to porsche engine performance it always comes back to the questions "where do you want to make your power?" and "how much do you want to spend?"

[KobaltBlau]

Adding to what Alan said...

First off, I don't believe that the Carrera 3.2 intake is much better than the CIS intake, especially the 39mm ones. Some people say the 3.2 intake has uneven flow characteristics to the runners.

With the 3.2 intake, you don't need all the cool injector mounting stuff tbitz has done, such as the injector sleeves and fuel rails/mounting. I'm not sure you would save any money, though. The basic kit has all of the unique stuff I'm talking about, plus the ECU:

http://www.bitzracing.com/products/Partial_EFI_KIT/index.html

with the 3.2 intake, you only need the ECU aftermarket, plus maybe a few sensor mods. You could use MegaSquirt like tony does.

Here are a couple of recent threads regarding individual throttle bodies:

Alan's thread:
http://forums.pelicanparts.com/porsche-911-technical-forum/158454-mfi-throttle-bodies-turbo-injector-blocks-post1265029.html?highlight=mfi+efi#post1265029

My thread:
EFI injector mounting "outside the box"

I am slowly accepting that TWMs are probably the way to go for EFI and hot cams, although they still seem pretty darn expensive. For milder cams (Elgin Super C2, Webcam 20/21, or smaller), the bitz cis-efi is okay, or a carrera setup. For that matter, CIS works OK with those cams.

For the GE40s you have, I think the lobe separation and durations would probably cause poor drivability with a plenum manifold. However, I'd be happy to hear from someone who has tried something like this. has anyone tried to run 72-73 911E or 'Solex' cams with a plenum manifold? these are sort of similar to the GE40s.

This is a very cool idea but probably a long ways from "prime time" in a 911:

MFI Delivery Rates

Best Regards,

[KobaltBlau]

I just read Alan's post, and I agree with all of it.

Very interesting that the guy tried 'S' cams with the Carrera 3.2 manifold, I hadn't heard about that.

Originally posted by Alan Cottrill
I'd guess a lobe angle any narrower than 108' would give you problems with a common plenum.

This sounds reasonable to me. Of course duration is also a factor, but the cams with lobe centers narrower than that tend to have longer durations.

According to jlutejen's cam chart:



There is only 9 degrees difference in overlap between the GE40 and 'S' cams (48 and 57 degrees, respectively), with 5 degree wider lobe separation, 102 vs 97 for the 'S' cam. Actually, the solex cam has the closest overlap to the GE40s. You'll notice that the 964 and SC cams are at 113 lobe sep. John Dougherty from Elgin posted in another thread that he thought the separation on the 20/21s was wrong in the chart, and should be 112. All the plenum cams have overlaps 10 degrees or less, including the CIS T which has closer lobe separation but short durations.

This makes it pretty clear that the GE40s are likely to be a bad match with any plenum. I know you haven't asked about the GE40s yet, but they are a good cam, and what you have.

[Shuie]

What about the MFI stacks and throttle bodies? Is it economically realistic or a pipe dream? I know anything is possible with enough disposable income, but has anyone ever done EFI using a MFI intake setup?

[KobaltBlau]

Originally posted by Shuie
has anyone ever done EFI using a MFI intake setup?

Not that I know of. In that other thread Alan was talking about doing it with turbo injector blocks, which seems possible but not necessarily cheap. I haven't looked into the cost on those aftermarket EFI turbo blocks.

In my thread, I was talking about mounting injectors above the throttle body, on a fabricated structure like the guy did with the ALFAs. Response has been small, but it seems there might be drivability issues with that setup. I do know that the Jerry Woods madonna setup is like that, does anyone know if the Jerry Woods madonna setup has been used successfully on street cars?

Bottom line on the MFI stacks is this: you could machine some injector blocks to put under the stacks or use the turbo ones. You could also mount the injector above the butterfly. If you are good with a torch, the latter option might be quite cheap, but I'm not sure on the drivability. The former option might cost just as much as TWMs, which I detail the costs of in my thread. I'm not sure quite how much the injector blocks cost.

[KobaltBlau]

Here is the thread that Alan was talking about from the megasquirt board:

http://www.msefi.com/viewtopic.php?t=2773&highlight=carrera

he says "sprint" cams so I believe he was using RSR sprint cams with the Carrera 3.2 manifold. 'S' cams might do better, but conventional wisdom follows what Alan and Myself have said above.

[erobinson]

Would the intake reversion problem be as severe running hot cams with an intake designed such that it has individual stacks on each cylinder coming to a common plenum on each bank. The banks have seperate throttle bodies (maybe a salvaged VW piece?) and are only connected with the map sensor line and possibly an IAC line.

Just a thought... I know there are engine gods far greater than I out there....

Eli

[danielt]

I used the Carrera intake with SDS EFI kit to convert to fuel injection on an SC. Works very well. I have not dyno'd yet, but hope to soon. Here is some incomplete documentation on making the conversion:

http://home.comcast.net/~tisserand/SDS_Install.htm

[67nin11]

shuie, i have read about alfa guys using efi throttle bodys off late model street bikes with success. (and they were bragging how cheap they got them off ebay). i dont know the spec. but a gsx 1100 has a suprisingly large throttle bore... hope this helps

[Shuie]

Found something.

Anybody have any details on this engine? Looks like a 3.6 in the background with a similar MFI intake on it. I wonder who's handywork this is?

[emcon5]

I think that is Cam's engine.

Tom

[Shuie]

he posted that pic in an old thread about a 3.0RS MFI setup. I sent him a PM about it. I couldnt tell from the post if it was his. I hope its his, Id love to know how someone made this work.

[KobaltBlau]

Yes, I do remember that Cam used MFI stacks and has EFI, now that we mention it. I guess I'm forgetful already. I think his (resourceful new zealander) mechanic may have figured out how to make it work.

[KobaltBlau]

Yeah, search for "mfi efi" with user CamB and you'll get a bunch, including his dyno. His MFI stacks were bored out to 40mm (new throttle plates?), so they must have been the metal ones. The most specific info I could find on fitting the injectors was that the stacks had been machined, MFI injector holes enlarged. You can also see the brackets that someone has built for the fuel rail in the picture. This is similar to what tbitz has done with his kit for CIS.

[911-32]

I can put you in touch with his engine builder if you like - his name is Jon Waring. He trades under the name Rennsport in Christchurch, NZ. His website is www.hadleigh.co.nz - which is the site for his and his wife's boutique accomodation business. However if you search thru the site, you will see a picture of Jon's old IROC replica (with 350hp 3.5 litre Motec engine) and his garage. His email is Jon.waring@xtra.co.nz. If you contact him make sure to say "hi from Richard Bernau" - he's an old friend of mine and I'm sure he would be happy to help out.

HTH
Richard

[Shuie]

Thanks Richard!

[kenikh]

Post more info if you find any...