TWM fuel injection

[lineslinger]

Do any of you boys have any expereince with TWM fuel injection systems? I would be very curious to hear about your setup, powerplant, reliabillity, troubleshooting, initial assembly etc.etc.etc..... any and all info much appreciated.
Thanks,

Mark

[Daniel Jones]

I've been working with a guy in the Pantera club on a similar EFI project for my Pantera. He's made the tooling to cast up IR EFI intakes for Windsor and Cleveland blocks running iron 4V or aluminum Ford Motorsport high port heads but the approach is the same for any engine for which a Weber intake exists. Pictures of the some of the progress are located at:
http://www.bacomatic.org/irefi/irefi.html

It looks like you are local to me. If you'd like to discuss the project, I can send a telephone number.

Dan Jones

[cwmcobra]

Do a search on TWM or fuel injection and look for threads from Mohuska. He's got a sweet TWM setup on his West Coast. Or, send him an email.

Chuck

[RPRICE]

lineslinger, I think that the Texas Cobra Club has some of these units running. Post over on their site under the LOCAL CLUB header. I tried the Imagine setup for my bb, it is simular to the TWM except more polished. The EFI units run so much hotter than a carb unit that we could not control underhood heat. As the intake air temp rose, it would also change the computer (Electromotive TEC 3) settings. After 6 months and many dollars, we pulled the unit off and put on a carb. Engine never gets over 85c now, before 110-115c was not uncommon. Roush has been working on the TWM setup for there cobra crate engine program, but don't think they have released them yet. At the Tx CC event last month, there was a guy with the Hilborn EFI injection. I followed him on a poker run. No heat, backfiring, etc. Are you considering using a distributor or going full electronics. If full, here is one thing that I experiecne, even with the carb, since I left the TEC 3 installed as my ingition system. When cranking the engine it must turn over 4 full revolutions to orientate the crank trigger. If you press the accelerator or if there is any fuel left in the intake, it WILL backfire thru the carb or pipes. As during the first four revs the plugs are firing, but at not the correct time. If you are running a bb with scj heads, let me know. I'll send you the Imagine unit for you to play with.
Richard
Memphis

[lineslinger]

RPRICE,
Thanks for the info and I will check the links you mentioned. Were you ever able to determine why the FI setup created the excess heat as opposed to a carb? My assumption was always that with FI efficiency heat problems would be minimized not magnified. I am also researching running the FI setup on a 351W. I talked to Roush about the motor they are testing right now with an FI setup and was told they have yet to make any final decisions, saying they needed to log more hours on it before finalising any formulas. They speculated the cost for that engine to be somewhere around 14 to 15K.
Thanks for the details on startup, I know I would have gotten ambushed by that one. I'll try to stay in touch with you carrying my sack full of questions if thats ok with you.
Thanks again,
Mark

[RPRICE]

Feel free to email anytime. The EFI units actually run a lot hotter than carbs. That is how they become more efficient in burning the fuel. It is much more lean than carbs, therefore hotter. Read between the lines on Roush. More time equals more ******. That is why they have not released them yet. This is my opinion and no one elses, but I am not sure that the intake used for these conversions has long enough runners. If you look at the Ford 5.0, GM LS1 or 6, the intake runners are three or four times longer than what TWM or Imagine use. Detroit spends millions on such research for a reason.
Richard
Memphis

[Daniel Jones]

> The EFI units actually run a lot hotter than carbs. That is how they
> become more efficient in burning the fuel. It is much more lean than
> carbs, therefore hotter.

That's not an inherent characteristic of an independent runner EFI
system. In fact, most closed loop EFI systems use a narrow-band oxygen
sensor to trim the fuel around stoichometric (the mid-point between rich
and lean) during part throttle cruise and go to a pre-defined map when
wide open throttle. A friend runs an independent runner EFI system and
it runs no hotter than the 4 barrel carb that was there before. My guess
is your mixture or spark weren't set correctly. Also, be aware that lean
isn't necessarily hot if the timing is adjusted to compensate.

The advantage of TWM type EFI is due primarily to the independent runner
intake manifolding. On a 90 degree V8, there are adjacent cylinders
that fire consecutively. In a plenum intake, the reversion from one
adjacent firing cylinder fouls the incoming mixture of the next. Also,
flow in the intake runner flows both directions, due to valve overlap.
These two characteristics give a hot-cammed V8 it's characteristic rumbly
idle. With an independent runner intake, the reversion from one cylinder
is isolated from other cylinders. This allows one to run a larger overlap
cam but still retain a decent idle and low/mid range performance. I know
a guy running a Weber look-a-like independent runner EFI system on a 377
cubic inch Cleveland stroker (iron 4V heads with Weber lower intake manifold
and 48mm TWM throttle bodies) in his Pantera. He runs a 288FDP Crower solid
flat tappet oval track cam. Specs on that cam are 254/258 degrees at 0.050",
0.569"/0.580" lift with 105 lobe centers. That's a lot of duration and
tight lobe centers for a street car (he drives his Pantera to and from work
and also competes in a lot of open track events). With a 700DP on a Ford
aluminum dual plane intake manifold, it had a wild idle and wouldn't start
pulling well until 3000 RPM (Crower rates the cam range as 3500 to 7000 RPM
in a 351C). When he installed the independent runner EFI, the first thing
he said was "Where'd my idle go?". The idle quieted down so much that he
wants to install a bigger cam to get some rumble back (it used to set off
car alarms) and it now pulls 5th gear from 1500 RPM. Kirby also noted it's
tough staying off the 7200 RPM rev-limiter in lower gears.

Another advantage is that you can have equal length runners that can
actually be tuned to a particular resonant peak which is difficult to
due with a conventional wet flow 4 barrel carb plenum intake with short
and long runners. Actually, the equal length part isn't that important,
since you'll still have cylinder-to-cylinder variation (even with equal
length headers) due to the uneven firing order of a 90 degree V8 (unless
you run a flat plane crankshaft and 180 degree headers). By its nature,
resonant tuning at one frequency (RPM) tends to rob another. It's not
unusual for stack injection systems to have two different stack heights
to widen the power band. Some builders have also experimented with
different cam profiles or rocker ratios to match the different stack
heights.

> but I am not sure that the intake used for these conversions has long
> enough runners. If you look at the Ford 5.0, GM LS1 or 6, the intake
> runners are three or four times longer than what TWM or Imagine use.

Not a direct comparison as the the Ford and GM intakes are independent
runner. Look to a V8 BMW M5 for an IR EFI set-up. The runner length
is from the valve face to the bellmouth (not the butterfly, resonant
tuning is only viable at near wide open throttle) and is treated as a
Helmholtz resonator. The harmonic you wish to tune to and the RPM
you want to make peak power at determines the best intake tract length
and diameter. In general, the stack EFI systems are on the short side
which raises thr RPM at which it works best. In practice, it's not
terribly important and even a short stack height will make better power
at low and mid RPM.

Dan Jones