CIS to EFI kit - Page 17

ohecht · 06-05-2004, 05:00 AM

Tony,

Can the part throttle and WOT switches built in to the stock TB on CIS cars be adapted to signal MS for various modes, maps, or other mixture adjustments?

Olivier

magic930 · 06-05-2004, 05:55 AM

I was just investigating this question yesterday! Unfortunately the stock TPS is not a potentiometer but is only a set of switches so it has to be replaced. The ECU needs to know where the throttle is throughout the range.

tbitz · 06-05-2004, 05:56 AM

Quote:

Originally posted by ohecht
Tony,

Can the part throttle and WOT switches built in to the stock TB on CIS cars be adapted to signal MS for various modes, maps, or other mixture adjustments?

Olivier

No.

Mixture adjustmentes are done via MAP (manifold vacuum pressure sensor) and engine rpm. There is no need for for such switches to meter fuel.

tbitz · 06:08 AM

Quote:

Originally posted by magic930
I was just investigating this question yesterday! Unfortunately the stock TPS is not a potentiometer but is only a set of switches so it has to be replaced. The ECU needs to know where the throttle is throughout the range.

TPS is only used for "acceleration enrichement". Here the ECU looks to see how quickly you press the gas pedal and dumps a little extra fuel similar to how a carburator does it.

With my EFI kit the TPS is not needed, because the ECU determines how quickly you press the gas pedal by looking at changes in manifold vacuum. If the manifold vacuum changes quickly the ECU sees these changes and dumps a little extra "acceleration enrichement" fuel.

So with my EFI kit no TPS is need. I've been running this way for the last little while and it works great.

On page 5 of this thread I explain how this works and show experimental data proving the theory. Click on the link below if your interested.
No TPS

Cheers,

magic930 · 06-05-2004, 06:54 AM

What I meant to say was how it moves through the range. Interesting that your Megasquirt setup doesn't use it. I would think that there is a slight delay in manifold change compared to throttle position change if you were to hit the throttle hard.

tbitz · 06-05-2004, 08:06 AM

No delay. Check the data I posted on page 5 of this thread.

ohecht · 06-05-2004, 09:39 AM

I was thinking of a switch to some sort of extra enrichment if necessary, rather than for the base map, but you're right that it is probably not necessary.

Olivier

ohecht · 06-08-2004, 05:48 AM

Tony,

I found this info on MSII on the MS forum, and this is the first I heard they might make it an easy upgrade to the current MS.

With your knowledge of MS and the kit you have now, how easily do you think these features could be integrated in the future? A clear upgrade path is a real plus for me in any system, ans I would eventually like to also control a type of crank-fire ignition (probably Ford EDIS).

From MS forums:

Al has been silently working on MS-II, which is a plug-in daughtercard which replaces the MC68HC908GP32 with a 9S12C32 processor. One simply removes the GP32 processor on their existing MS and plugs in the MS-II daughtercard and their MegaSquirt is now a MegaSquirt-II - it takes less than a minute to do.

Al has it running on the bench and is working out code details as we speak.

MS-II will give the following:

- 25 MHz HCS12 processor (C32 version)
- Fuel control to 1 usec
- Ignition control (full advance, dwell, etc)
- on-board stepper motor driver for IAC stepper control (will require a few jumpers to be added on the MS main board to implement the socket jumers to the connector.
- Dual-tables for VE and AFR target tables (in AFR units)
- All tables now at 12 x 12, can be increased to 16 x 16 if wanted.- CAN *may* be added in next revision of hardware
- Very inexpensive (still working out the cost with CM assembly).

Al is getting close on this for first testing, so we should have more info real soon.

- Bruce

Olivier

klatinn · 06-08-2004, 07:09 AM

Hi Tony,

Does the MS sample MAP synchronous with the engine cycle, for example at a fixed crank angle?
The reason I'm asking is because with hot cams the intake reversion can create a false MAP pulse, that, when sampled at the wrong time, can cause an upset of the mapping.
I imagine this would be specially a problem at low RPMs.

Regards,
Klaus

tbitz · 06-08-2004, 07:00 PM

Olivier,

If it is just a matter of replacing the CPU, then it should be a very simple upgrade path. I'm also looking forward to this MSII.

Klaus,

MAP is most likely sampled once during each ignition event. Where that occurs, I don't know. You can always run the vacuum signal to a small plenum to average out the pulses if that's a problem.

ohecht · 06-11-2004, 08:18 AM

Tony,

Will my car still make the cool "wump" sound (AAV closing?) when I start my car with this kit?

If not, can I program that into the fuel maps? I love that part of my day each morning!

Olivier

tbitz · 06-11-2004, 12:52 PM

Quote:

Originally posted by ohecht
Tony,

Will my car still make the cool "wump" sound (AAV closing?) when I start my car with this kit?

If not, can I program that into the fuel maps? I love that part of my day each morning!

Olivier

If you don't plan on hacking up the airbox, then the AAV can be left in place.

Cheers,

tbitz · 06-19-2004, 09:51 AM

My car is fairly well tuned, but I still like to look at the sensors once in a while. The laptop is a little bulky for this job, so I picked up an old Palm Pilot IIIc for the job ($80 CAN).

It allows you to display info and make changes if needed. The laptop has more features, but with the car tuned you don't really need them.

I am going to find a way to mount it so it doesn't come fly during high G turns.

The display on the Palm IIIc is a color TFT display similar to modern laptops. And best of all its touch screen! It looks very cool in the 911 cockpit. I feel like I'm in a F-16

The display software is written by a fellow in the megasquirt forum. It is written in BASIC and is very easy to customize if you have some basic programing knowledge.

ohecht · 06-20-2004, 09:34 AM

Any chance something like this could be used in the future to switch between two different fuel maps or other settings? like a "economy" mode for long highway trips and a power mode for windy roads and the track?

I know maps can be saved and uploaded with the laptop, but the Palm idea seems closer to something you could switch almost on the fly.

Olivier

tbitz · 06-20-2004, 09:54 AM

You don't really need two maps (economy and power).

The reason is, you tune the table so at WOT you're optimizing for power and at part throttle you tune for economy. One map can do both. If you want to save gas, you simply don't go WOT.

irnwill · 06-20-2004, 03:36 PM

Looks much better than a laptop on the passenger floor. What type of cable did you use to plug into the megasquirt?

tbitz · 06-20-2004, 08:09 PM

The older Palm Pilots used a serial interface to comunicate. All that is required is to flip the Tx/Rx wires between the Palm and the Megasquirt. This can be accoplished with a "null modem" cable.

abisel · 07-29-2004, 05:59 PM

So what is the latest on your system?

Have you started looking into a system for the earlier MFI cars?
My project is a 2.8 RSR engine. I thought about going the original RSR configuration (MFI and dual dizzy), but am thinking of newer technology.

I do have some suggestions on your current system:

It looks to me that the fuel rail mounting brackets are prone to failure. The combination of fuel rail and brackets has no upper support. With constant vibration, the lower bent part of the bracket will eventually crack and the fuel injector(s) could work their way out of the bung. You might want to look into an upper support to secure the assembly to the runners to keep it from vibrating inboard and outboard.

Can you provide a lamba readout that is dash mounted? Along with this, provide a fine tuning pot to adjust the F/A mixture on the fly. Tricking the ECU to thinking it is running rich will result in a shorter pulse at the FI, thus leaning out the engine. Or visa versa. So, with a pot in the O2 sensor output (input to the ECU), you adjust the O2 input voltage of the ECU, you then could effectively adjust the mixture remotely.

On another note:

EGT is another way to adjust fuel mixture. High EGT means a lean mixture, lower EGT means a rich mixture. A normal EGT would be between 1300 F and 1600 F. In the general aviation world, once a pilot has established his cruising altitude, he would adjust the fuel mixture to a peak EGT, and then richen the mixture to about 25 F cooler. This is described as optimum economy for a Lycoming engine. For optimum performance, adjust the mixture for an EGT temperature 100 F cooler than peak. The same could be said the 911 engine. Monitor the EGT, adjust the mixture to peak EGT, then richen the mixture to a lower temperature for either economy or performance.

BTW, CHT is a good way to observe if a particular cylinder is operating at peak performance. A normal CHT would be around 350 F. Monitoring both EGT and CHT for a particular cylinder, you could diagnose a problem as it occurs. For example, if the EGT was high and the CHT was low, you could have a burnt valve, broken ring, bad plug or wire. If the EGT were high and the CHT high, you could have a plugged fuel injector or an air intake leak. High EGT and CHT = excessively leaned engine, detonation from bad fuel, missing cooling baffles. Low EGT and CHT = rich engine.

So, when I get around to it, I plan to install GEM engine analyzer to monitor EGT and CHT at each of the 6 cylinders. It may be a bit costly (aviation instruments can be costly), but talk about assurance on how the engine is performing and being able to catch a problem before a catastrophic failure.
http://www.seaerospace.com/insight/gem602.htm

tbitz · 07-29-2004, 06:35 PM

abisel,

Thanks for the suggestions.

I have no current plans for a kit for the earlier MFI cars.

The the fuel rails are rock solid in the current configuration. There is no latteral movement. The three brackets together with the three injectors make the system very solid. I don't think another upper support would do anything more.

Lambda readout can be dash mounted. Just look above to earlier posts. I am using a palm pilot to display key parameters.

No need to trick the ECU with a pot. You can just re-program on the fly the target O2 switching point via laptop. This is the beauty of MegaSquirt.

CHT, EGT and all the avaition gauges are cool, but come with a big price tag. You have to be real hard core to have 6 EGT and CHT monitors in your 911.

Cheers,

abisel · 07:03 PM

Quote:

Originally posted by tbitz

Lambda readout can be dash mounted. Just look above to earlier posts. I am using a palm pilot to display key parameters.

No need to trick the ECU with a pot. You can just re-program on the fly the target O2 switching point via laptop. This is the beauty of MegaSquirt.

CHT, EGT and all the avaition gauges are cool, but come with a big price tag. You have to be real hard core to have 6 EGT and CHT monitors in your 911.

I understand the ability to change the O2 switching point via laptop, but that isnt very safe when you are driving down the road. Palm pilot either. A simple twist of a knob would be better don't you think?

As for the EGT/CHT, I have heard of people saying that their 911 has hot and cold running cylinders.

Does the ECU have inputs to monitor EGT/CHT?