Independant throttle body , EFI , management questions

With EFI, the P6 cams would be much more tame on the street than with carbs. Porsche guys run P6-like cams on the street with mechanical injection and they do well. Matter of fact, the early 911s engine had stock intake cams with the same duration as a P6 cam! As for your other questions I am not entirely sure. I am sure someone does!

 

The intake runners will still see vacuum at anything other than WOT.

The MAP sensor doesn't change that, it simply reads the vacuum/MAP.

I would try to get vacuum signal from more than one intake runner. My car has vapor recovery plumbing under the carbs that I would try to use for MAP if I go EFI.

You will need a cam, and crank, or dizzy signal (single dizzy setup) for timed sequential. I suppose you could have untimed sequential, but the pulses would have no relation to intake opening and would change every time you started the car.

EFI can be programmed to cover up a lot of cam duration, that would otherwise make the car essentially undrivable at low RPM. A trip to knowledgeable dyno tuner is worth the money.

Doug

 

BTW, when I switched to sequential from batch fire on my Chev, the difference was glaringly apparent, the car ran so much better under 1500 RPM with sequential, with my 230/236 duration (duration measured at .050" lift) cam, Actual duration is 280/288 at .006" tappet lift.

Doug

 

full sequential is a PITA! phased is far easier and a step between batch and full sequential. you'll only need the crank signal. idle issues are only when the injector is too big for the application and can not meter down enough at idle and will run a bit rich. match the injector and you're good. low impedance have better response than high.

for the MAP signal collect a signal from at least each bank or if possible from each throttle body, then run them to a single volume chamber to equalize the pulsed signal, from that chamber pull your MAP signal. the shorter the runs the better as the long runs will reduce response time for proper fuel metering. also you'll need to run a bias towards the TPS at idle to compensate for the MAP signal.

 

With ITBs you uyse the MAP for barometric pressure, but you'l want to tune with the TPS, it will be much easier to tune this way.

I disagree with Scott ont he sequential, I won't use anythiong else these days. i also have a new rule about not using any ecu that doesn't have at least individual cylinder trims...you just never know when you're going to need it for whatever reason.

 

An M48 will be perfect.

You want teh Map because ever day to day pressure changes atter.

Waste spark is fine.

 

MAP is also very important for part throttle fuel economy, as it is used to adjust your spark advance at higher manifold vacuums, sort of an ersatz vacuum advance. You can also use it to adjust your feedback AFR so at cruise, you are running say 15 or 16:1 AFR at 50% MAP, while at WOT, you may want 11.8:1 AFR. It is the difference between 14-15 MPG at highway cruise vs 18-19 MPG at highway cruise.

Doug

 

I only consider full sequential to be a pain due to the increased parts and setup and not that necessary for builds where power and performance over fuel economy are a concern. at a certain point in RPM, not recalling off the top of my head right now, the injector duty cycle between phased and sequential is negligible. only because of the milliseconds of time delt with.

for the average user taking advantage of sequential can be very time consuming. cylinder trim is a great benefit of that but you need to really understand what you're doing to avoid damage.

In my opinion going with a std. phased setup will get you way ahead of CIS and you'll still be able to get good MPG.

for the TPS vs MAP sensor. if you don't use a speed density system that utilizes the MAP, MAT and various other sensors you'll need to use a mass-air setup.
Otherwise, having the TPS signal the only input is a bit of a misnomer, the ECU is in reality offsetting the voltage signal of the MAP to 'fool' the ECU into seeing a stable Hgmm reading. the TPS is also calibrated from idle stop to WOT stop to get a voltage sweep for the calculation. On some of the more radical or individual throttles I bias the to the TPS till about 2500rpm then it's back to MAP voltage.

EFI can get very techy!
I think Mark just likes to add complexity for the pure gruesome pleasure next he'll be building a flux capacitor!

 

TPS or MAP its still speed density and both sensors are 0-5V so the only think the ECU really does is display TPS instead of MAP on the tuning table.

There are some advantages and some draw-backs to TPS tuning. On he plus side the you get much better resolution near WOT than you do with a MAP sensor and it doesn’t care about long duration cams and bizzaro pulses in the manifold and doesn’t care that the pressure signal is not continuous (ITBs). On the down side the TPS is probably the least reliable engine sensor and they tend to drift as they wear so you end up needing to re-tune every couple years on a street car, every few months on a race car.

I like the idea of the “blend” setting a lot of ECUs have where you can use the TPS at low and/or high rpm and the MAP everywhere else but you still need to deal with the TPS drift and I personally think it’s a bigger problem in this type of set-up. Anytime you have 2 sensor basically controlling the same thing (load) they need to be matched and when the TPS drifts you lose that matching and start to get a bit of a discontinuity in you tuning maps.

If I ever get my ECU finished I’m planning to program it to read 2 MAP sensors mounted to cylinder that are 360 degrees apart and use window feature to only allow readings from the sensor in the specified time window which can be tuned to each rpm point…I think this will allow a clean MAP signal with ITBS and hot cams. We’ll see....if nothing else it will be more complicated and use extra parts so it will be better for that if nothing else

 

Here's a site with a basic overview of the types of EFI.
http://www.fordfuelinjection.com/?p=4

Alpha-N is TPS based only and not something I'd put on the street. Speed density has to use both TPS and MAP to meter the fuel as the TPS is the 'load' sensor for the ECU.

 

Kind of a crazy question, but in the vein of simplicity would it be possible to modify a CIS unit into a different type injection system with individual throttle plates and ditch the sensor plate? Yeah I know it wouldnt have all the bells and whistles of an EFI system, but it could be just about bulletproof.

 

We were talking a little about this on another thread. You could pull the sensor plate but you'd have to add an actuator or some kind to move whatever the plate is connected to. Basically would buy a cheap ECU and hook it up, but instead of the output running electronic injectors you connect it to the actuator. TI would look stock for the CA smog Nazis, but give you control, make more HP and let you run and cams, turbo or whatever.

 

I don't know why. Non sequential works perfectly well on my car and many others...

Theoretical or experiential reasons?

 

That's a VERY basic overview…with a lot of it so simple it boarders on just plain wrong.

On the ECU I’m working on the plan is to build in a lot of the limp-home stuff the OEMs have. One of those features is to let a speed density car run alpha-N if a MAP problem is detected or an Alpha-N car run speed density if a TPS problem is detected. Both systems need and use both the TPS and MAP sensors to work properly so it’s just a question of adding an additional tuning map and you get a ton more peace of mind knowing you can get home. When you are in this limp-home mode and running ONLY the MAP or TPS the descriptions given in the link you posted would be pretty much all correct, but for general, proper operation not so much.

Not exactly. Alpha-N uses the TPS for load and acceleration enrichment and a MAP for barometric correction. Speed density uses the MAP for load (which is auto corrected for barometric differences because pressure is pressure) and uses a TPS for acceleration enrichment. TPS is pretty much always used for acceleration enrichment because it’s a leading indicator, ie the throttle must be opened BEFORE any acceleration can occur so you can the extra fuel there. Acceleration enrichment can also be done using the MAP change rate but there is a lot of noise in the MAP signal so you end up with some lag while you try to filter out the niose.

As I said above, a proper working speed density or Ahpla-N system need both a TPS and a MAP because neither system works very well without a lot of the features of the other added to it so they end up being almost exactly the same thing with just some subtitle differences that would make you go one way vs. the other. There shouldn’t be any way the driver could tell which system is running the engine from the driver’s seat (I tried this experiment with 1 car and 3 or 4 drivers, no one could tell).


Speed density is always my 1st choice for a street engine because it is more time stable (TPS sensors drift a bit with use and vibration) and very accurate at low power but. You would get a little better fuel mileage starting and stopping around town where the closed loop is not active with speed density but highway mileage with closed loop active the results would be about the same as A-N.

Alpha-N is better able to deal with very hot cams and lack of a plenum. For example P6s cams with TWM TBs in place of the webers would probably be an idle candidate for Alpha-n control. I’ve really never seen any ITB set-up work very well with anything but A-N because short of multiple MAP sensors and a windowing technique there is just no way to get a clean MAP signal and even this would need to look at the TPS to know what is happening between the reading windows to keep things working right during acceleration. When I first fire it up my engine with the ITBs it will be an A-N for sure and may stay that way forever because A-N works the best with ITBs and pretty good over-all. I’m going to spend some time screwing around with trying to figure out how to get speed-density working with the ITBs (the windowing I talked about) mostly because I like the challenge and not having to even check the tuning ever again, but it won’t really bother me if I end up with A-N forever because even with the MASSIVE full race cams, the HUGE full race ports, the ENORMOUS 54mm ITBs and the Very large Tube and Very short length headers the engine should still idle and drive better than a stock engine

 

Practical.

I completely agree with you that plain old multipoint injection( which is the electronic equivalent of CIS without the limits of CIS) works just fine on most applications…..but personally as of this past summer I have complete sworn off ever even touching another engine with this set-up.

Full sequential injection works better than multipoint on EVERY application, not always a lot better, but always noticeably better. Any engine set-up for full sequential can run multipoint and I’ve done the experiment on a few different engine where I tune but sequential and multipoint and you can always tell the difference in back to back testing. Full sequential makes the engine run smoother and will use less fuel which is why it has been the only OEM systems since the mid 90s.

The nexted thing is you get more hp with sequential. Yuo can run larger injectors that run at lower duty cycles and that always yields more hp. HP is good.

None of that is why I’ve sworn off non-sequential though. I’ve work on 2 cars I the past few years that after screwing around for hours and hours trying to get the low power mixture right I realized the problem was in the engine not the electronics. When you are running multipoint all the mechanical parts need to be matched, and in batch or semi-sequential the parts on the same channel need to be matched. What’s happened to me a couple times now is the engine I was working on was a bit tired so the vacuum was not the same in all the cylinders….so cruising or at idle 1 cylinder would be way rich, one so lean is barely ran and the rest somewhere in between. The right thing to do would be rebuild the engine but that is a tough pill to swallow in the middle of a several thousand dollar EFI conversion…..with full sequential you just trim the cylinder on the cheaper ECUs or individually map the cylinders on the better ECUs and the engine runs right. This problem gets masked on carb or ITB cars where to vacuum match the cylinder before you start tuning, but on plenum engines there is no way but individual cylinder fuel control to deal with it......plus the more hp so it's a win-win.