Help with building your Speeduino, installing it, getting it to run etc.
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By jonbill
#44157
hi, I'm installing Speeduino in a supercharged Toyota 1zz engine. its the first boosted engine I've played with and I'm a bit surprised by what I see from the MAP sensor. on full throttle upto 4k rpm I haven't seen MAP values over 100kpa, but even at idle I can see the inlet tract before the throttle is well above atmospheric pressure.
is this reasonable? is the engine able to consume the greater volume of air, or is my MAP wrongly calibrated or is my BOV just not closing?
all thoughts, experience and ridicule welcome!
By justthetim
#44158
I'm new to engine tuning... so the advice I'm offering below is what I would do to get to the bottom of this.

1. The speeduino MAP senor can read up to 250kPA here is the spec sheet

https://www.mouser.com/datasheet/2/302/ ... 127330.pdf

Get a cheap syringe, plug in your MAP sensor line, and use the syringe to increase the pressure in the MAP sensor line, you should be able to get it above 100kpa.

Also, if you have a spare pressure gauge, connect it in-line to check that the MAP reading and gauge are accurate.
Do this with the engine off.

2. If you do have a spare pressure gauge, find a spot to connect it after the supercharger. That way you can visually check the MAP readings.

*you can steal a pressure gauge from your air compressor, but the reading wont be very accurate, since your compressor gauge will be 0-200psi..
User avatar
By jonbill
#44160
Thanks, that made sense, and I've done that test. with my syringe I can get the speeduino MAP sensor to report even 250kpa.
I connected a cheap boost gauge at the output of the supercharger.

At 3500 rpm (unloaded):
speedy map sensor was showing about 30kpa
speedy TPS shows about 6%
the boost gauge shows 0.7 bar boost (so thats 170 kpa?)

is that reasonable? I would expect the pressure in the manifold with a 6% open throttle and 0.7 bar boost to be rather higher :?:
User avatar
By jonbill
#44164
it's an Eaton M45. I'll see if I can get the pulley ratio. I suppose with that we can work out how much air the engine can pump at my 3500 rpm and see hopefully that stacks up against the air the supercharger puts out.
is that the idea? thanks for the help.
User avatar
By jonbill
#44165
the charger pulley is 120mm and I believe the crank pulley is 130mm, so the ratio is 1.08.

I think an 1800 cc engine pumps 222 cfm at 3500rpm, whereas the supercharger inlet flow in your link at 3500*1.08 rpm is about 100,
so does that mean its reasonable for the manifold to still be at or under atmospheric pressure?
By fins
#44199
I agree that that pulley ratio sounds way off; the Eaton m45 has a swept volume of 737cc/rev, so a ratio of 1.08 would give 798 cc/rev, short of the "base" ammount of air required , 897cc (i.e. 1/2 the displacement).
User avatar
By jonbill
#44202
thanks guys, at least that confirms my map sensor is right and the manifold pressure can't exceed atmospheric with this pulley.
I've got a 90mm pulley (so 1.44 ratio) to play with, but I think I'll finish mapping it with this one first and see how it is.

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