LH2.2 and LH2.4 AMM signal modifications

As many of you know, installing Browntops or versions of CFI injectors on LH2.2 requires some modifications. Namely adding a resistor in-line with the AMM signal going to the ECU.

This modification can be read about in the thread: How to install Brown Tops on LH 2.2!


And this is also an AMM modification that can be applied to both LH2.2 and LH2.4 taken from my FAQ thread:

Q: Can I use a bigger AMM to run higher boost?

A: Using a bigger AMM on LH2.4 is also a great way to extend the ability of higher boost. The 3" AMM off a 91-94 960 with the last three digits 012 works on 99% of all LH2.4 ECU´s. Since this AMM is bigger than the stock AMM, you will need to match it with larger injectors. The percentual increase in cross-sectional area when going from a stock 016 AMM to a 012 AMM needs to be matched with an equal percentual increase in injector size.

You can also match bigger injectors with a custom size AMM to get the proportions right. Use the internals of a stock or 960 AMM and put them in a larger pipe. The ideal size for the AMM at your intended boost level can be optimized by measuring the voltage across pin 1 and 3 at full load. The AMM should show 5.0v at 1000rpm before the rev-limit (5.0v at 5250rpm if you use LH2.4). If the voltmeter show 5.0v before that rpm, the AMM is too small. And if the volmeter doesn´t show 5.0v until after that rpm, the AMM is too large. This is a fine balance between AMM and injector size but it will surely be rewarding once set up right.

LH2.2 users may not have many options of a bigger AMM unless you put the stock internals of the stock AMM in a larger pipe, or if you find an LH2.2 vehicle of another brand with a larger size AMM that works. (Addition: Lately it seems as though a 006 AMM from an LH2.2 equipped B280F car actually works)

Except for the fact that you have to run proportionally larger injectors with a bigger AMM, you can also increase the injector size even further just like on the stock AMM. An increase of up to ~30% in flow over the calculated size may also work with the larger AMM.

All changes in AMM size will also result in slightly more advanced ignition timing. Always keep that in mind if you are doing a modification like this. Watch out for knock/ping.


Lately we have been discussing AMM size and possible modifications. And that is why I have started this thread...

Let's clear some things up regarding signal modifications.

The contents in this thread will eventually be added to my FAQ.

First of all, 10% change in reported flow from the AMM to the ECU is ~0.1v at the end of the AMM's useful metering range (the end of its metering range is here referred to as 4.5-4.95v even though the AMM can report a much higher voltage).


LH2.2:

To keep as much linearity as possible in the flow reported to the ECU it is highly recommended to put the 007 AMM electronics in a bigger tube or use a 006 AMM.

Either way you go with LH2.2 you will probably need a resistor since LH2.2 is not as adaptable as LH2.4.

You can still use very large resistance values with LH2.2 since the ignition timing is adjustable, so the use of very big injectors is really not a problem to set up.

When putting a resistor in-line with the signal going from the AMM to the ECU, the ignition timing will also change (it will be more advanced). Please be careful when setting the ignition timing. Preferrably retard the distributor a couple of degrees before doing this mod, then set the timing to where you want it after the mod has been done and tried out.

Q: Where do I put the resistor?

A: Between pin 3 on the AMM and pin 7 on the ECU.



Q: Which value should I use on the resistor for my injectors?

A: First of all, that depends on what the impedance/resistance is in the ECU. Measure the resistance between pin 6 and 7 on the ECU. The resistance should be close to 10 kOhms or 25 kOhms.

If your ECU has a resistance of ~10 kOhms, then these values will be useful (approximate values, may differ slightly):

5% change in reported flow: 118 Ohm
10%: 237 Ohm
15%: 348 Ohm
20%: 475 Ohm
25%: 590 Ohm
30%: 715 Ohm
35%: 845 Ohm
40%: 976 Ohm
45%: 1.1 kOhm
50%: 1.24 kOhm
55%: 1.4 kOhm
60%: 1.54 kOhm
65%: 1.69 kOhm
70%: 1.87 kOhm
75%: 2 kOhm
80%: 2.15 kOhm
85%: 2.32 kOhm
90%: 2.49 kOhm
95%: 2.67 kOhm
100% (double the stock injector size): 2.87 kOhm

If your ECU has a resistance of ~25 kOhms, then these values will be useful (approximate values, may differ slightly):

5% change in reported flow: 294 Ohm
10%: 590 Ohm
15%: 887 Ohm
20%: 1.18 kOhm
25%: 1.47 kOhm
30%: 1.78 kOhm
35%: 2.1 kOhm
40%: 2.43 kOhm
45%: 2.8 kOhm
50%: 3.09 kOhm
55%: 3.48 kOhm
60%: 3.83 kOhm
65%: 4.22 kOhm
70%: 4.64 kOhm
75%: 4.99 kOhm
80%: 5.36 kOhm
85%: 5.76 kOhm
90%: 6.2 kOhm
95%: 6.65 kOhm
100% (double the stock injector size): 7.15 kOhm


Remember: The more resistance you put in-line with the AMM signal, the more skew and inaccuracy you will also put on the signal.


LH2.4:

To keep as much linearity as possible in the flow reported to the ECU it is highly recommended to put the 016 AMM electronics in a bigger tube or use a 012 AMM (even the electronics from a 012 AMM may need to be put in a bigger tube).

After some investigation and looking deep into this matter, it has been found that you can use resistors to alter the AMM signal on LH2.4 as well. But... only for adjustment and fine-tuning. Around 30-35% of change in the AMM signal is tolerable for adaptation.

When putting a resistor in-line with the signal going from the AMM to the ECU, the ignition timing will also change (it will be more advanced). Please listen carefully for pinging when doing a modification like this.

Q: Where do I put the resistor?

A: Between pin 3 on the AMM and pin 7 on the ECU. If you also put a Zener diode between pin 6 and 7, then put it before or after the resistor as shown in the picture below. If you put it after the resistor you may have to use a different voltage and current draw.



Q: Which value should I use on the resistor for my injectors?

A: First of all, that depends on what the impedance/resistance is in the ECU. Measure the resistance between pin 6 and 7 on the ECU. The resistance should be close to 10 kOhms or 25 kOhms.

If your ECU has a resistance of ~10 kOhms, then these values will be useful (approximate values, may differ slightly):

5% change in reported flow: 118 Ohm
10%: 237 Ohm
15%: 348 Ohm
20%: 475 Ohm
25%: 590 Ohm
30%: 715 Ohm
35%: 845 Ohm

If your ECU has a resistance of ~25 kOhms, then these values will be useful (approximate values, may differ slightly):

5% change in reported flow: 294 Ohm
10%: 590 Ohm
15%: 887 Ohm
20%: 1.18 kOhm
25%: 1.47 kOhm
30%: 1.78 kOhm
35%: 2.1 kOhm


This modification will benefit both NA and turbo cars with LH2.4. The NA cars may get a nice boost in performance from the altered injector size and added timing as well.

A modification like this is also very beneficial for running alternative fuels like E85 or LPG since they can benefit from the added timing a lot. Expect a nice bump in performance.

And... going to the dragstrip and also using race gas will be more fun.

[mike nz]

I can confirm that a 006 AMM works on my LH 2.2 car as a replacement for a 007 .. though it was extremely lean on initial start up, some judicious turning of the mixture screw soon got it running ..

On the dyno it still proved to be dangerously lean but adjustment of the FPR fixed that best it could be .. but the operator is adamant that its less than ideal, he says the AFR`s were all over the place .. a bit lean at the bottom end, OK thru the midrange and rich at the top end .. varying from his recollection between about 13.5 to 12.0. The car was 13rwhp down on power from the last time with the 007. He again told me the same thing he`s been telling me for 5 years .. that to truly benefit it needs a stand alone .. but the car was safe but not ideal ..

This was at 18psi on avgas.

At the drags following day I went faster than ever before .. 14.1 @ 99.98 (!!) as opposed to 14.3 @ 97 .. both with a tailwind and interestingly with no difference in the 60` or 1/8 times.. however this was more likely as a result of the previously untried 4.1 `s .. then the trans died .. but from water contamination not hp ..

Of course I am now wondering whether the trans slowed me up and whether it was responsible for the lower rwhp .. we`ve got 1/8 mile street drags this weekend and 1/4`s the following .. that will tell I`m sure ...

Cheers Mike

I have been out tonight to fine tune my car a little.

Some smoothness was gained, but I gained a ****load of torque from the added timing.

I settled at around 15%, but I have to drive around for a few days to see if that is ok.

[v40jlt4]

Hi Fred,

Is it possible (and usefull of course) to combine the possibilities of the bigger AMM and the resistor mod?
Or is that pointless?

I mean, If stock injectors are 32lb but I plan on using 52lb, can I
1) use a 012 AMM to compensate for about 20% to accept 39lb injectors
2) do the resistor mod for the remaining 33%?

BTW, I remember the last time a resistor in the AMM signal mod was proposed. Several heads were bitten off.

[JW240]

Very nice mod, the results sound promising! i cant wait to go back to E85 with bigger injectors

Originally Posted by v40jlt4

Hi Fred,
BTW, I remember the last time a resistor in the AMM signal mod was proposed. Several heads were bitten off.

yup i remember that as well.

Originally Posted by v40jlt4

Hi Fred,

Is it possible (and usefull of course) to combine the possibilities of the bigger AMM and the resistor mod?
Or is that pointless?

Yes, that is the idea here actually.

Originally Posted by v40jlt4

I mean, If stock injectors are 32lb but I plan on using 52lb, can I
1) use a 012 AMM to compensate for about 20% to accept 39lb injectors
2) do the resistor mod for the remaining 33%?

The 012 AMM is made for running 450-465cc/min injectors.

52lb/hr is 546cc/min.

To adjust the injector flow, you need to lower the flow by ~20%.

Originally Posted by v40jlt4

BTW, I remember the last time a resistor in the AMM signal mod was proposed. Several heads were bitten off.

Adjusting / fine tuning with resistors is ok and works as long as you stay within the adaptability of LH2.4. You can not add resistors and adjust for very big injectors (i.e. 500-ish cc/min) on the stock AMM.

On LH2.2 you can go much further with resistors.

On both LH2.2 and LH2.4 it is highly recommended to adjust the injector flow with AMM size and fuel pressure as much as possible, and then do the fine tuning with resistors if neccesary.

[BDKR]

Great show Fred! Keep it up and you'll be Turbobricks Jak Stoll.

I'm going to keep a link to this fer shizzle. At this point in time, I'm working on tranny isses, but this is going to go a long ways.

[HonestJhon]

i just did this last night.
played with a few settings.
and it does seem to advance the timing a bit. and definately need to keep an eye out for ping.
however, with 5% correction, the 65lb/hr injectors no longer bog at ~10 PSI.
gotta drive a few days to see how it does. but it felt really strong last night, and i wasnt even really flooring it. (kinda scared of blowing it up) gonna try and figure out MAF scaling with size as well, then adjust a bit.
i made an inline quick disconnect for the MAF harness, and put a small perf-board with the diode, and resistors on it, and made solder traces. put it in a project box, and zip tied it to the maf plug wire.
easy to pull out of the car and go back to "stock" and easy to pull out and change the resistors. if i was to do it again, i might make it with a dip switch selector, and varying resistors. that way i wouldnt have to unsolder resistors and do it again.
also, with the advanced timing, i MIGGGHHHTTT make the methanol come on earlier...
if it starts at 8psi, and scales up to full on at 14 psi, it should be good.


another thing i noticed, is the car likes to boost creep more now. maybe it was cause it was colder last night when i was driving it, but it went up to 18 PSI a few times, kinda made the hair on the back of my neck stand up.

[lammmy]

So, excuse my ignorance, but is this mod exclusively for use with bigger injectors, or is there any sort of benefit to be gained with stock injectors?

I was going to run to PnP this weekend to get a new AMM anyway, since I suspect mine of sucking.

[500dollar744ti]

after my most recent experiences with lh2.2 i would not recommend going over the 600ohm mark... i had 65lb injectors with 1250ohms in the amm line, this caused the ecu to pull too much timing under boost resulting in severe piston killing detonation.

[joe reese]

im curious if this mod will work with lh 3.1 ? i would like to put my cam in my 91 240 5sp and set it up to run e-85, i know that it wouldnt be good to +t this setup,but cam,bigger inj, e-85 ?

[PetesDustyVolvo]

Originally Posted by 500dollar744ti

after my most recent experiences with lh2.2 i would not recommend going over the 600ohm mark... i had 65lb injectors with 1250ohms in the amm line, this caused the ecu to pull too much timing under boost resulting in severe piston killing detonation.

Just for future reference of people discovering this thread, "pulling" too much timing would have left you with no power and would definitely have not been a contributing factor in the destruction of your pistons. When people say "pulling timing," I generally assume they mean retarding the timing.

Basically, your ECU thought there was a lot less air-flow than their actually was, so it calculated a spark timing which was too advanced. Bigger, more compressed mixtures detonate faster. It also didn't help that you were running a higher static compression ratio.

According to my timing map, 15+ psi, on 91 octane gas, with volvo 9.8:1 SCR pistons, you're talking single digit BTDC spark advance numbers.

Wild ass guess, your ECU was probably delivering 10-15 degrees too much advance. Even 1-2 degrees too much will make it ping.

edited for clarity... i'm still having my morning coffee

Originally Posted by joe reese

im curious if this mod will work with lh 3.1 ? i would like to put my cam in my 91 240 5sp and set it up to run e-85, i know that it wouldnt be good to +t this setup,but cam,bigger inj, e-85 ?

I think with E85 you could just throw proportionally bigger injectors in there and call it a day. Maybe even jumper the ECU for a bit more spark advance.

[MikeSr.]

This has been discussed before on the board regarding LH 2.4. Somebody( with a Supra?) has used a variable resistance potentiometer inline with the AMM signal to accomplish the same thing. He tuned the WOT AFR using this, and LH learned the idle spots. Seems like that would be easier to adjust the resistance values than switching different fixed resistors.

[BDKR]

Originally Posted by MikeSr.

This has been discussed before on the board regarding LH 2.4. Somebody( with a Supra?) has used a variable resistance potentiometer inline with the AMM signal to accomplish the same thing. He tuned the WOT AFR using this, and LH learned the idle spots. Seems like that would be easier to adjust the resistance values than switching different fixed resistors.

Yeah, it was Kris Weldy.

[BrickBorg612]

Originally Posted by MikeSr.

This has been discussed before on the board regarding LH 2.4. Somebody( with a Supra?) has used a variable resistance potentiometer inline with the AMM signal to accomplish the same thing. He tuned the WOT AFR using this, and LH learned the idle spots. Seems like that would be easier to adjust the resistance values than switching different fixed resistors.

I really like this idea, I was thinking about it earlier today actually. Thought I was being original lol. Got a link to the car?

[BDKR]

Originally Posted by BrickBorg612

I really like this idea, I was thinking about it earlier today actually. Thought I was being original lol. Got a link to the car?

There you go.

http://forums.turbobricks.com/showth...upra+injectors

[lammmy]

Originally Posted by 500dollar744ti

after my most recent experiences with lh2.2 i would not recommend going over the 600ohm mark... i had 65lb injectors with 1250ohms in the amm line, this caused the ecu to pull too much timing under boost resulting in severe piston killing detonation.

I thought the ECU had nothing to do with timing on lh2.2...

[PetesDustyVolvo]

Originally Posted by lammmy

I thought the ECU had nothing to do with timing on lh2.2...

EZK needs some sort of load signal. Where else is it going to get it other than the MAF?

Now LH 1.0 on the other hand....

Originally Posted by lammmy

So, excuse my ignorance, but is this mod exclusively for use with bigger injectors, or is there any sort of benefit to be gained with stock injectors?

No, you can't do the mod with stock injectors. It will run too lean.

Originally Posted by joe reese

im curious if this mod will work with lh 3.1 ? i would like to put my cam in my 91 240 5sp and set it up to run e-85, i know that it wouldnt be good to +t this setup,but cam,bigger inj, e-85 ?

Yes, that will work.

[BDKR]

OK. Stupid question time. Based on the below....



How do I know which pin is pin 3?

Thanx

[Booster]

If your trying to do something with the amm, the pins are labeled on the harness/ pigtail / connector itself.

with the amm connection facing you from left to right it's (6,5,4,3,2,1)

Posted via Mobile Device

[BDKR]

Originally Posted by Booster

If your trying to do something with the amm, the pins are labeled on the harness/ pigtail / connector itself.

with the amm connection facing you from left to right it's (6,5,4,3,2,1)

Posted via Mobile Device

It's funny, but after posting that, I figured it might be.

I'm here at work so I didn't go outside to check.

Thanx

[BDKR]

OK, what happens if you put a resistor on the 2 wire?

I guess I'll have to fix it this afternoon.

Strange thing is that the mixture is better and it's doing everything you would hope for. In my case, that includes increasing the timing since I'm running a grooved head and can do so safely.

Originally Posted by BDKR

OK, what happens if you put a resistor on the 2 wire?

I guess I'll have to fix it this afternoon.

Strange thing is that the mixture is better and it's doing everything you would hope for. In my case, that includes increasing the timing since I'm running a grooved head and can do so safely.

That would probably also offset the signal since the reference ground is skewed. But that is not recommended since it will give other effects as well.