Tuning with CIS - Page 4 - PeachParts Mercedes-Benz Forum

gsxr · #46 03-09-2009, 05:22 PM

Quote:

Originally Posted by pentoman

This isn't right (if we're talking about a KE sytem).

Sorry, Eric and I were talking about LH injection - not the same as KE. My apologies for the confusion. I have edited that post to clarify things.

Quote:

Originally Posted by pentoman

I believe Jay is right about the standard 6 degrees retard - it's documented pretty well on the infamous 'free hp for w124/w201 owners' thread. What's also documented well though is mixed results (in terms of noticeability) when it comes to returning it to 0 retard.

This is where I get highly skeptical. The presence of a resistor does not indicate there must be some retard. However the lack of a resistor does, I think, force maximum retard (minimum power). That "free HP" thread was a steaming pile of BS, IMNSHO, at least for USA-spec cars. I pulled the resistor on my '86 300E and watched my fuel economy drop 10% while gaining absolutely zero power. This trick may work in other countries which did have some amount of retard from the factory (so if you set it to less, or zero, retard there is a power increase). But for USA-spec vehicles, I still think we got zero retard (max power).

I also suspect the source of this myth is the difference in octane ratings between Europe and USA. People mistakenly think that because Europe has 96-100 octane premium pump gas, while the USA has 91-93 octane premium pump gas, that USA cars got "de-tuned" via a different EZL resistor setting, for our supposedly "low octane" gasoline. This is NOT TRUE... if you research RON and MON octane ratings, and the numbers displayed at the pumps on both sdes of the pond, you'll find that their gas and our gas is basically the same. One (or the other) does not have magically better pump gas.

JayRash · #47 03-09-2009, 05:59 PM

gsxr is correct abt the fuel rating. I say usa has same grade fuel as the best in other countries. I might suspect that california cars might be slightly detuned, cant be sure as i live out of the usa.
Thats up to u guys to confirm. As for noticing more power, well u need to try and coax more timing to really feel it. Hence the temp trick. Dont forget a few degs of advance go a long way. But am sure u might hear some ping on top rpms if u really go crazy with the resistor values. I know i did.

Gr8 forum guys i love it.

RBYCC · #48 03-09-2009, 06:22 PM

Quote:

Originally Posted by gsxr

I seriously doubt that USA-spec cars came delivered with 6° of retard. Do you have any documentation to prove that? AFAICT, US-spec cars came with zero retard (full power).

If I recall the R16 resistor value in a USA spec car is 750 ohms.
This would equate to a 6 degree retard.

Agree that pulling the resistor on a stock vehicle really makes no noticeable difference in performance.

It does however make a difference on a turbo vehicle.

gsxr · #49 03-09-2009, 06:43 PM

Quote:

Originally Posted by RBYCC

If I recall the R16 resistor value in a USA spec car is 750 ohms.
This would equate to a 6 degree retard.

Agree that pulling the resistor on a stock vehicle really makes no noticeable difference in performance. It does however make a difference on a turbo vehicle.

Pulling the resistor increases retard, right? Which I understand may reduce detonation under boost, but on a normally aspirated engine, it would actually cause a power LOSS instead of a power gain.

I'd still like to see factory documentation that shows 6° retard for a resistor value of 750 ohms (as well as for the other half-dozen values). The FSM (click here to view PDF file) doesn't seem to jive with those values, at least for CIS injection on the M103...

400Eric · #50 03-09-2009, 06:45 PM

Don't forget G-man, I'm a M-103 guy too!
I tested the 24 81 resistor and it gave me 749 ohms (within the tolerance I'm sure). Now I think it has been fairly well documented that when the 750 ohm spot is chosen on the cars that have those cool dials, the EZL retards the timing by 6 degrees. I think U.S. cars got the fixed 6 degree retard simply for emissions reasons. You and I briefly touched on the "resistor mod" topic before (in a PM I think) but I didn't really state my opinion because I didn't want to seem too argumentative cause I like and respect you too much but I have to say I'm a believer. I intend to back it with some back to back ETs in the future. It seems that the gain is mostly under part throttle conditions and low to mid-range RPM which make sense cause that is where the advance is needed the most and where these engines are kind of "soggy".
Lots of other posts to respond to but I'll have to do it later tonight. Regards, Eric

gsxr · #51 03-09-2009, 06:50 PM

Eric, hey, I have no problem being proved wrong!

But while 750 ohms may indeed provide 6° of retard, I strongly believe that infinite resistance (resistor removed) does not provide zero retard (i.e., max power). So what I'd like to know is, what resistance value is needed to pick up those elusive six degrees?

400Eric · #52 03-09-2009, 07:10 PM

The problem is I don't have the ETs yet to prove my point so I just let it lay.
As far as the info goes I think it is here: READ!!! Free HP for W201 & W124 owners! (Pictures!) Just be sure to not skip anything and read everything on every link (yeah, it's gonna take a while but I think the info you want is in there somewhere).
Oops, I just realized that this is the thread you refer to as a "steaming pile of..." but somewhere in there is a post or a link from a guy that shows the actual number of degrees of advance and at what RPM the M-103 receives that advance with and with-out the 24 81 resistor. Regards

pentoman · #53 03-09-2009, 07:15 PM

Quote:

Originally Posted by gsxr

Pulling the resistor increases retard, right? Which I understand may reduce detonation under boost, but on a normally aspirated engine, it would actually cause a power LOSS instead of a power gain.

I'd still like to see factory documentation that shows 6° retard for a resistor value of 750 ohms (as well as for the other half-dozen values). The FSM (click here to view PDF file) doesn't seem to jive with those values, at least for CIS injection on the M103...

Happy to think it's false, but I believe I have some proof... here http://www.hamsk.ru/murzik/KE-jetronic/WIS%20Test%20data%20KE.pdf
bottom section of page 3

or http://www.hamsk.ru/murzik/KE-jetronic/EZL.pdf middle of page 3

but it isn't totally conclusive. To cloud measures the second link appears to have a translation issue and has a W instead of an ohms symbol but those W readings coincide with my own resistance measurements for this trimming plug, apart from position A -1W I believe this should be an infinity symbol as infinite resistance is what is found on my car's plug at that position (and 1 ohm seems very unlikely given the 0 ohm reading at the opposite G position of the scale...

teezer · #54 03-09-2009, 09:34 PM

i'd like to chip in ~~~ eliminating the resistor definitely made a difference in mine, no more cold off idle flat spot and more responsive acceleration

as an old hot rodder and playing with timing from the 50's to the 80's. i've watched the timing go from @10 degrees advanced to 0 to @7.5 retarded, mainly to pass emissions. total timing ranged @28 to 32 but could be pushed to 36-40, but this was done on a mechanical distributor with springs. needless to say they always run a bit better with an advance bump

anyone know the total advance spec on the m103?

if 0 is all you can get by eliminating the resistor, can you get another 5 or 10 by playing with the top dead center sensor or the repositioning of the cam gear?? and would this affect total timing, as controlled by the brain ??

gsxr · #55 03-09-2009, 10:15 PM

Quote:

Originally Posted by pentoman

Happy to think it's false, but I believe I have some proof... here http://www.hamsk.ru/murzik/KE-jetronic/WIS%20Test%20data%20KE.pdf
bottom section of page 3

or http://www.hamsk.ru/murzik/KE-jetronic/EZL.pdf middle of page 3

but it isn't totally conclusive.

Ah, now that is interesting. Note that in the first link, it is the non-catalyst version where infinite resistance (no resistor) translates into full advance (zero retard). But for the catalyst (KAT) version, full advance requires a 750 ohm resistor!

For an English version of the second PDF, click here. Unfortunately that document doesn't specify what each of the 7 position does, it just says what resistance should be used, and the values for the standard setting.

It also appears that things could have changed around the 1988/1989 model year, which may explain why my 1986 300E lost power & economy with the resistor removed, while other people (presumably with newer models) experienced a power gain.

400Eric · #56 03-09-2009, 11:55 PM

My 88 and 89 love the mod. There was another change starting with the 90MY and it seems there are a number of those guys that aren't as excited about the mod either.

RBYCC · #57 03-10-2009, 12:02 AM

Quote:

Originally Posted by gsxr

Pulling the resistor increases retard, right? Which I understand may reduce detonation under boost, but on a normally aspirated engine, it would actually cause a power LOSS instead of a power gain.

Pulling the resistor advances the timing 6 degree as the 750 ohm resistor is what creates the 6 degree retard.
I want more timing on my TT as my AFR averages 12.8 and under full boost it's 11.8:1
Seven pounds and I dyno'd 302 torque at the rear wheels on a load dyno.

Quote:

I'd still like to see factory documentation that shows 6° retard for a resistor value of 750 ohms (as well as for the other half-dozen values). The FSM (click here to view PDF file) doesn't seem to jive with those values, at least for CIS injection on the M103...

This is from my M103 engine manual..
Pull the resistor and read the timing and you'll end up with six more degrees advance...

400Eric · #58 03-10-2009, 12:10 AM

Quote:

Originally Posted by pentoman

I am very surprised to hear this. This means the early R129 500SL came with KE Jetronic too? I have taken your information and tried to prove it for myself. I am surprised if when designing the M119 they bothered with KE at all, knowing they were moving away from it only 2-3 years later.
Wasn't the 600 from 1991 and it did not have KE Jetronic?

Googling some pics of the 1990 500 engine I found this pic

Is that a fuel distributor at the back? Does that mean it's KE?

and this pic of a 1993

which does not have that.

If it's true shouldn't this mean a 1990-1991 500 engine would have a lot worse power/torque curve than a 1992-? Which hopefully brings us close to topic..

I thought the V-12 came out in 92.
Yes it is. Yes it does.
No. The CIS-E makes good power and torque it just can't match the good emissions and fuel economy of a good sequential FI system.

400Eric · #59 03-10-2009, 12:32 AM

Quote:

Originally Posted by JayRash

i have to check again, been ages since i read them, and i might have done it as u say. once i check ill let u know, p/n 015 545 08 28 / 9251 06

on a sad note i blew a piston ring on my TTm103

Sorry to hear about this but I believe you can't keep a good car down and you can't keep a good man down. You'll bring her back. Regards, Eric

400Eric · #60 03-10-2009, 01:06 AM

Everyone, see updated post #52 above. Eric