z-ya

Actually, you can. You just need to make sure that the MAP sensor voltage range matches that of all the ADCs in the processor. Most all processor have a single ADC reference voltage, so you just need to tailor the sensors output voltage range to match that of the ADC. I think for most all people that use the 250kPA sensor, this is fine. When people use higher pressure sensors, and then just start entering kPA numbers in the VE and spark tables, bad things can happen. The table does display kPA as the units, when it isn't. To me, this is broken. Either take the kPA off the VE and spark tables in MT, or fix the firmware to do the conversion. It can be done with a simple lookup table in the firmware. My $0.02.

I totally agree. There are 256 "voltage" steps (0-255) from 0V to full scale on the input of the ADC. The MAP sensor converts pressure to voltage. The circuit in the MS translates the MAP sensor output voltage range to match the ADC input voltage range (or at least it should) to maximize dynamic range. The firmware then uses a lookup table of some sort to convert voltage levels to actual pressure which the interpolation algorithm uses. This is how I think it should work (then I did a little testing). The firmware I'm running (Extra code 029v) appears to limit the max kPA value to 255 no matter which sensor I have selected under "Engine Constants". In my mind this should be a bug as the maximum value you can enter in the VE or spark table in the load band column should equal the max boost your sensor supports. If this is truly the correct behavior, then you would need to think of it as an 8 bit number like TimZ said, and do the scaling in your head. Again, this does not seem right. Why not have the processor do this math for you (unless MS1 with extra code and a 12x12 table does not have the cycles to do this computation in real time). Make sense?

You should pop a spark plug and shine a flashlight into one of the cylinders. If they are dished pistons, your CR is too low for an NA. Flat tops with a P90A head make for a nice street-able engine with hydraulic lifters (quiet, no valve adjustments)

You are correct, the ADCs on the 8 bit processor are 8bit in resolution. This not all that important to the end user because the voltage range from the MAP sensor is scaled to match the input range of the ADC. Based on what MAP sensor you tell MS you are using, the software will do the appropriate scaling.

Why do you guys care if the processor is 8 or 16 bit? MSI uses and 8 bit processor, and MSII uses a 16 bit one. Extra code gives you a 12x12 table, and from my experience the 8 bit processor has enough cycles to handle it. It is when you start running boost control, water injection, etc. that you might start running out of processor cycles. Yes, it takes the last VE table entries and extrapolates up. The nice thing about the MS is that you can customize your load and RPM range scale to fit the application. The highest load range bin should be the max boost you plan on running plus a few kPA for some headroom. For NA, it should be 100. The lowest load range should be the minimum pressure the engine operates within minus a couple kPA, not your idle pressure. Many engines will make more vacuum under other operating conditions besides idle. Especially if you are running a non stock cam. For a stock turbo cam, the idle pressure is more than likely the lowest.

Do you mean an IAC? Are you using the fidle output for your coil? If not, use that to control your IAC relay.

What are you trying to do?

Thanks for posting. Great article. After many years, I still get excited about Megasquirt.

It depends on what pistons are in it. If they are dished, it is a turbo motor. If they are flat, and have "P79" stamped in them, then somewhere along the line the head was swapped. The P79 head is identical to the P90, except that it has round exhaust ports with liners.

The most difficult part of setting up a knock sensor is tuning the audible sound that you engine makes when detonating. Different engines have different knock frequency characteristics, so it comes down to more than just amplitude. This is why off the shelf units that tune the sensor, to the control box is a good solution. They also have tuning capabilities. Car makers spend many hours tuning their knock control systems.

Have you verified your timing with a timing light? At idle, check your timing in the Wolf, it should match what you measure with a timing light. If it doesn't, you can program a timing offset into the Wolf so that you timing table entries match your actual measure timing. It sounds like your actual timing is advance from your timing table. You should be able to run 25deg all day at 15psi with a stock L28ET long block.

The twin TBs are really just for a different look on a twin turbo setup. This is what I am leaning towards. I'm going to start mocking things up. The biggest challenge will be the exhaust manifold. There is a lot of other work besides just welding in there. It took a lot of time to machine both the EFI flange and the SU manifolds so that they joined squarely. The welding part took the least amount of time. The prep work took about 6-8 hours. The smoothing after the welding is also very time consuming. Cost? Find out what you local welding shop charges by the hour. I have a bartering relationship with a metal fabricator, so he does all my critical welding.

I'm still in the process of deciding what motor to put it on (NA, turbo, twin turbo). as soon as I make more progress, I will post it.

Does your engine have a P90A head? When cold, they can make some noise if you have a lifter that is marginal. As it pumps up with oil and heats up, the clatter should stop.

I have a good fuel only N47-F54-NA base map for turbo injectors if anyone is interested. Run a stock Nissan head gasket. If you run a metal one, and continue to have detonation problems, you will be replacing more than the head gasket. The head gasket is a good safely fuse. Hear is what happen to my SC motor with a metal gasket and detonation: http://forums.hybridz.org/showthread.php?t=128000 Plus why lower the compression ratio. You just need to spend some time tuning to get the advance and AFR right. On high comp NA L6 motors I've tuned them around 13:1 AFR, with 25-28deg max advance. This will produce good power (180WHP on my last build) on northeast 93 octane pump gas.

Are you using wideband O2? With 30lb injectors, you will not have any idle problems, so go ahead and use a different target AFR than 14.7:1. In either case, keep increasing the VE table bins until you get the AFR your looking for. I've run VE bin entries over 160 without any issues.

Since you are a student now, and on a limited budget. I would get the L24 tuned and running well in near stock form just for use as a daily driver. A well tuned stock L24 has plenty of pep for daily driving, and you can get upwards of 30mpg. Save your money and built yourself a hot L28 when you can afford to do it right.

I think the shaved marker look great, but at night the OEM markers look pretty cool.

If you set the required fuel based on your full boost AFR, the pulse width may be too wide to get a proper fueling a low engine loads (depending on how large an injector you are using). I usually set the required fuel for 14.7:1, and then adjust it to get a smooth idle. Then adjust the VR table to tune across all other operating conditions.

Have you ever hear a Camden SC at 6500+RPM? You can't hear much else. All you can hear is the SC coming up through the TB. We dyno tuned it conservatively. My guess is that on the dyno the intake air temps never came close to what they did on the track. So it was detonating, and we couldn't hear it over the SC. Those old Camden superchargers are great at making heat. Plus I was running it dry. Having a couple of injectors upstream of the impellers would have cooled it a bit. Not a good setup for a track car, especially if run dry.

Yes, the pistons we installed correctly. The damage is on the hot side (driver). Heat, detonation was the cause.

Finally had a chance to pull apart the SC motor that lost compression on 3 cylinders. Specs: - L28, std bore, stock P79 pistons - 2mm metal gasket - 8.1 CR - Camden supercharger 8psi boost - Dyno tuned to 11.5 to 12:1 AFR - Advance at 8psi ~20deg - 255 RWHP - Intake temps reached 280F on a regular basis during track sessions It held together for almost two time trial seasons. It failed on the way back to the pits after a session. Still was running, but on only three cylinders. The crank looks to be fine. So hear are the results: Piston 4: Piston 5: Pistons in order 1,2,3,4,5,6, Note all skirts broken on one side:

You can reuse the used rockers. Find used rockers that don't have a ridge worn in them. Or you can send them out to be reground at Delta Camshaft. I think they charge $3 each to regrind them. They look like new after the regrind. You must swap in the correct lash pads to obtain the correct wipe pattern for a given cam. If you assume they are correct, you can severely damage the cam and rockers almost instantly.

Sounds like something might be binding in the pedal mechanism, booster or the MC. Disconnect the pedal from the booster and see if it moves freely.

I didn't see the logos on the Porsche, cool. Eddie is into high performance cars. I think he met Sammy Hagar through their mutual Lamborghini mechanic.