2.4T MFI - Not a complete dog?!

[dtw]

Ever since I went out for a blast in Tim's Flying Turd, I can't get the engine out of my head. This was a 2.4T MFI running on 5 cylinders, out of tune, and blowing smoke on every shift. Yet, it was a damned fast car and very rev-happy. It is the first 2.4T I've driven, and I have no frame of reference. I can't supply any quantitative data, but my butt's impression is that this motor rocks? It blew away all my expectations. Pulled strong to about 5750 and then flattened out, I think due to the 5 cylinder/tuning issue. 3500-5750 was pretty unbelievable for a small displacement motor.

Is it possible Tim's motor has been massaged, because I am having a hard time believing what I drove was a stock T. I'm going to be pouring sand in his intake next time I see the FT to kill that motor once and for all- I want to see those cams and pistons.

[jluetjen]

Dave;
It's hard to tell given the 5 cylinder thing, but it doesn't sound like that rev range is unreasonable since a 2.4TE's quoted rev range (peak torque to peak HP) was 4000 RPM to 5600 RPM.

I strongly suggest that you NOT take a ride in an E or an S since either of those two cars (with working MFI) will dangerously expand your horizons.

Like I've said on other threads, once you've experianced MFI, there's no going back.

[Tim Walsh]

HAHA!!! Well it's not official yet but I think we'll be seeing those P&C's sooner than I want.

If what I've driven is a stock 2.4T with "only" 140 hp, I'll be more than happy with it. Even with crappy seats adn tires, no alignment and a motor running WAYY too rich and with a dead hole the car is/was more fun than anything I've ever driven. I can't wait to get her reliable and running right. I just have to wait to build up the cash reserve for the rebuild.. ohh the life of a student

Dave,
We did bounce it off the revlimiter at 6500's so it very much might be a stock T.


edit: I've driven a fairly well sorted our E (david clarke's) and it really does have a fair amount more power than my T but I think the T isn't a slouch either.

[David E. Clark]

I'm loving my "E." Great power and very rev happy, but for the price --I've seen reasonable "T's" in the $5,000.00 range -- you gotta love the MFI "T!" I don't think you can find a better Porsche fun per dollar car.

Tim, did the "water decarbonizing" or anything else help the FT's black hole?

David Clark
'73 911E

[Tim Walsh]

David,
I don't think it helped much since when I drove it back home home just before I went to WI she took a turn for the worse. She lost a little bit of oil pressure (down to about 12psi @ 2K),started smoking and her oil temp went up more than I've ever seen it (only about 215F).

Right now I"m looking into options on how to rebuild her. I hoped to avoid the rebuild but it looks like that will be the only way to have any sort of piece of mind and have her running right.

[dtw]

John, it's going to be a fun juxtaposition if I ever get my two engines built. One is going to be about as nasty as a 2.4 can get on pump gas and single plugs, the other is going to be a stock T. I'm going to experience the range of fun of the 2.4 ...supposedly the stock T engine came with "E" cams, but I haven't verified this. Hopefully this will turn out to be true and I'll have a little extra kick in the pants. All said and done, I'd be thrilled with a stock T for a daily driver. What a motor! I absolutely can't wait to get mine built.

I'm hoping my hotrod motor will be sufficiently unruly and undriveable as to not spoil me for the stock motor...if it turns out to be a nice linear motor that's happy to idle, the T will no doubt be up for sale...and I don't want to do that (don't worry, won't happen).

[Tim Walsh]

Dave,
we can make sure it's undrivable.. just stick in some 906 cams

[arrivederci]

One of the previous owners of my T rebuilt it with 2.2S P&Cs. It still has the T cams, the T MFI pump, etc. See the dyno sheet on my website, along with a video of the dyno runs. FYI: 145 rwhp. Notice how flat the torque curve is. It keeps up with stock carreras on straight aways at DE events.

http://members.rennlist.com/jpinkert/porsche.htm

[Tim Walsh]

The car definitly has T cylinders. So could it be possible for them to install 2.2 pistons in the T Cylinders?

[dtw]

Yup. The difference in the 2.2 and 2.4 is a change in stroke, not bore.

The installation of 2.2 pistons has been a popular upgrade according to BA. Per my own investigations, it doesn't make much sense anymore- good used 2.2 pistons are impossible to find, and JEs can be had brand new for under 1k.

[Tim Walsh]

hmm.. but I'd wonder about interaction between the cast iron cylinders and the pistons. Would that be compatible? My initial guess is yes but I'm a relative newbie.

[304065]

Josh, interesting point.

Stock 2.2T = 2249#, 125 HP = 17.99 lb/hp
Your 2.2T = 2249#, 170 HP = 13.23 lb/hp

Stock Carrera = 2756#, 200 HP = 13.78 lb/hp

Above assumes stock weight and equivalent driver weight.

I race against some guys in PCA who whoop a$$ in stock-class T's. If the momentum can be managed they are capable of some pretty impressive lap times.

[Jay Auskin]

Tim--if you're doing a rebuild, I keep hearing that the euro 2.7 P&C's are the way to go w/ an "S" cam. I can't speak from experience, but everyone who's done it raves on and on. I believe the euro 2.7 P/Cs are cheaper than stock 2.4 T P/C's. If I need a rebuild (I pulled the motor out last weekend) that's definitely the way I'll go!

[Tim Walsh]

I'm not so sure about the 2.7 P&C's if my pistons are out of round I think I'll go with boring out my T cylinders. My case is a 3R/4r case so it's not very strong at all and I'd be worried about overstressing it with the larger cylinders. The other part is that if I go with the 2.7 I'll have to recalibrate the MFI pump and as a student I don't have that much to spend. Once I tear into it then I can set up a definite plan for it.

[jluetjen]

If you go up to a 2.7 you'll have to strip the engine down completely so that the spiggots can be bored for the larger 2.7 cylinders. If you have to remove the studs before the case can be bored, then your into possible time certs, line bore, etc. etc. etc.

If I were you and I were just doing a top-end rebuild I'd get some EBS pistons with 9.5:1 CR (at least 1.0 more then Euro 2.7's). Since you have iron cylinders, you could even get the cylinders bored out to 85mm and have "2.3" if your car has a 66 mm crank or "2.5" if your car has a 70.4 mm crank. I suspect that the piston price will be the same. Don't worry about the piston material having any problems with the iron cylinders, iron cylinders is the "traditional" cylinder material used in 90% of the worlds engines.

If you don't want to touch the MFI, I'd keep the same T cams. If you want to spring to have the MFI pump recalibrated, you could get E cams and have an engine that will pull through 7000 RPM.

[Tim Walsh]

John,
I have both a 66mm crank and a 70.4mm crank, but I think what I will build if everything goes right (includeing the $$) I would like use to use the 70.4mm crank, bore my cylinders out to 85mm put S cams and 9.9:1CR pistons in it and recalibrate the MFI pump. That should make a 195-200hp screamer.

[zotman72]

I took my 72 2.4T MFI motor to 2.4 S MFI. I kind of wish I did the 2.7MFI but still have the option next time around.

[Tim Walsh]

Bill,
Did you change your pistons or both your p&c's?

[Halm]

Tim, Just out of curiosity, do you have any idea how much $$$ you are talking about to build this "screamer"?

[jluetjen]

l33t9eek;
I just noticed that you have a '72, so that would mean that you have a 70.4 mm crank in your engine. My point was that I wouldn't want to mess with the crankcase if I didn't have to since it would introduce a whole list of issues which may be fine now, but will need to be fixed if you crack the case.

Regarding upgrading your engine to 2.4S spec, sure that would be a cool engine, but I'd recommend that you port the heads out to 36 mm from the 32 mm intake ports in your T heads. That may also mean opening up the MFI throttle bodies to match. I've gone through the intake gas speeds for most of the factory 911 configurations, and the 2.4E had about the fastest gas speed of them all. A 2.4S with 32 mm intake ports would most likely run just like a 2.4 S until 6500-7000 RPM when the intake ports would choke off the engine. It would be fun while it is "on-cam", but the usable torque rev range would be reduced by about 500 - 1000 RPM.

An E cam on the other hand will out pull an S up through 3500 RPM. It's only at 4000 RPM and above that an S cam exceeds the E in torque. Given the amount of additional money to make an S, an E with 85mm P&C's and a 9.5:1 CR might be a great compromise.