Tuning Difficulties - Help needed!!

[mhandx1]

Having spent the weekend installing MicroSquirt & GSX-R TB's (40mm) on my friends Pinto 2l engine 146bhp@6500 133ft/lb@4300rpm got the engine started ok but running very rich 10.9 on the wideband. Not 100% on the MAP sensor readings that I am getting (GM Sensor) reading 5volts full scale (260kpa) engine off, 147Kpa at idle and going up to 160kpa at higher TP openings. Does this seem right due to low vacuum pressue or do we need to rescale or configure the MAP sensor & settings? Checked for leaks etc but all ok(using the GSX-r vacuum points commoned up).

Due to the above the VE, AFR & Spark tables are only ploting across the top 100Kpa bin and not ploting anywhere else causing our problem, I have not adjusted the KPA bins in the tables as I do not think we have enough range on the MAP sensor to give adequate control. Am I correct to think this??

Started to look at Alpha-N but my brain turned to jelly at this point! selected Alpha-N in config & MegaTune ok but the first thing that threw me was the bins in VE,AFR & Spark stayed on KPA rather than change to TPS, is this correct? I am at the point now where I think the Alpha-N map table converts /calculates TPS into KPA value for use in the tables.... If this is the case how do you calculate what KPA you have to corresponding RPM in the table estimator??? more important how do you check without going on the rollers?

Having read several threads and manuals I am suffering from information overload being new to this so any advice or "misinformed person" guides to the problem would be greatly appreciated.

Many thanks,

Mark.

[Matt Cramer]

Something is wrong with your MAP sensor. Check it with a volt meter. If you're getting 5 volts with the engine off, something is very wrong with the sensor.

[mhandx1]

Hi Matt,

Thanks for a reply.

The Map sensor is a GM unit off a N/A car 2.0l couldn't cross referance the GM part number 2503679 from the manuals with a UK car or parts suppliers, but with some cross referencing we came up with part No: MS002, (going to double check this again now).

The map sensor we have is giving 5 volts with no vacuum applied and with mouth suction I can pull it down under 1 volt. I suspect from your reply this should be the other way round??

Looking at the MicroSquirt manual wirining section I have connected as per the GM sensor connections "A" Ground "B" Sensor "C" +5 Ref but there is also another diagram prior to the GM connections that shows connections "A" & "C" the opposite way round, could having "A" & "C" the wrong way be causing our problem and will it blow the map sensor if I swap the polarity??

Mark.

[TheMonkey]

Mark-

I think you have things right getting 5volts with engine off. but.... i think you need to calibrate your sensor.

I pulled a 1 bar GM map sensor off of a late model NA motor. My settings in MT are 5 volts = 104.5kpa. engine off is about 98 kpa here. 0 volts set to 10.1 kpa.

most people with MS use 2 or 3 bar sensors which have much lower voltage when engine is off.

1 volt on my sensor is probably about 30 kpa, or about 25-30" of vac (guesstimate). that's a pretty big straw, but probably possible to take drink of water through one.

to calibrate your sensor, go to 'tools', then to 'sensor calibration'. sounds like you have a 1 bar sensor, so 5 volts kpa setting will probably be similar to mine (104.5). you can try my 0 volt setting of 10.1 kpa, but if i was you, i would use a hand vacuum pump with reading of inches of vac to calibrate it properly.

sounds like right now, your settings are setup for a 2 or 3 bar sensor.

[TheMonkey]

For reference.... here are some readings i picked up. i just went through this yesterday, to match a new MAP sensor readings with my previous one that is was spec'd with MSII on V3.0 board.

sorry for the columns being messed up, but first column is vacuum in inches: 0 - 22.5; second column is kpa reading from MT; 3rd column voltage reading from stock sensor on V3.0 board as delivered from DIY; fourth column is voltage from 1 bar map sensor pulled from junkyard.

inches ---- kpa reading ---- volts from MSII sensor ---- volts from 1 bar GM map
0 ---- 98.2 ---- 1.8 ---- 4.6
5 ---- 80.0 ---- 1.4 ---- 3.7
7.5 ---- 72.3 ---- 1.2 ---- 3.3
10 ---- 62.3 ---- 1.1 ---- 2.8
12.5 ---- 54.2 ---- 0.9 ---- 2.3
15 ---- 46.5 ---- 0.7 ---- 1.9
17.5 ---- 36.2 ---- 0.5 ---- 1.4
20 ---- 27.1 ---- 0.4 ---- 1.0
22.5 ---- 20.4 ---- 0.2 ---- 0.5

so, it seems also that 1 volt on my sensor is 20". that might seem about right for what someone can suck with lungs. hmm.... now i feel like i want to try it. my son is a swimmer, maybe i'll have a contest with him.

[mhandx1]

Hi Monkey,

Thanks for the information the readings you have sent are very helpful, going to grab the Druck from work the weekend to Cal the sensor.

If anyone reading this has tables for VE, AFR & spark advance that they could send me or point me in the right direction to find them I would be grateful.

The spec is 2.0l Pinto 146bhp @ 6500 rpm - 133ft/lb @ 4300rpm
GSX-R TB 40mm with 250cc injectors
EDIS on ignition.

I have used the table generate function but it seems to generate some very high and low numbers in the the tables which I am not very trusting or confident of.

Many Thanks,

Mark.