I need advice on fender rubbing issues, tire width is stock.
10-31-2012, 10:21 PM
#26
Well you could but you'll want to keep a close ear and keep in mind the stock one the setup is tuned for, 760 ohms and US pump grade fuel is probably matched to your particular cam part number (it's stamped on the cam gear, there are several that were used), so is suitable for your engine in your region under all common conditions.
Switching to the 440 ohms may seem fine until you hit some hot weather or go into higher elevation and then start pinging. Going to 1.3k ohms might seem okay until after a time it starts to flat spot under certain conditions.
In any case it's a subtle difference and not really about more power, that's just not going to happen at this level of modification, it's just fine tuning and more about drivability response.
The main thing which changes when you play with the spark advance is you just move the torque curve up and down the rpm range. The idea is to match with spark what the mechanicals are trying to do, that includes things like manifolding and valve timing as well as cylinder temps and fuel/knock.
So the setup which gets you the best performance is the one which is most accurately matched to the specific engine setup/fuel type, not the most advance. More isn't always better.
Induction harmonics and flow rates start working best in mid range on these engines anyway, M102 or M103, they like 3500-5500rpm and work best there. So you can't have too much spark advance on the stock setup to start with because you'll be bringing the ignition harmonics down to low rpm, and the engine needs it up the range.
Switching to the 440 ohms may seem fine until you hit some hot weather or go into higher elevation and then start pinging. Going to 1.3k ohms might seem okay until after a time it starts to flat spot under certain conditions.
In any case it's a subtle difference and not really about more power, that's just not going to happen at this level of modification, it's just fine tuning and more about drivability response.
The main thing which changes when you play with the spark advance is you just move the torque curve up and down the rpm range. The idea is to match with spark what the mechanicals are trying to do, that includes things like manifolding and valve timing as well as cylinder temps and fuel/knock.
So the setup which gets you the best performance is the one which is most accurately matched to the specific engine setup/fuel type, not the most advance. More isn't always better.
Induction harmonics and flow rates start working best in mid range on these engines anyway, M102 or M103, they like 3500-5500rpm and work best there. So you can't have too much spark advance on the stock setup to start with because you'll be bringing the ignition harmonics down to low rpm, and the engine needs it up the range.
11-01-2012, 03:01 AM
#27
Member
Thread Starter
well the reason i want to move the torque a small amount down the power band is because in a large city like phoenix i need it down low for stop and go traffic as the off the line with this car is horrendous. (again, a '91 2.3-8v with 195k miles on it)
11-01-2012, 03:08 PM
#28
Member
Thread Starter
I also just noticed that the mounts that attach to the valve cover for the air box have broken free. what adhesive should i use to reattach these to the valve cover?
11-01-2012, 06:54 PM
#29
On my engine they're rubber dollies that screw into the intake manifold, which screws into the dollies. If the rubber separates replace. Age/heat makes rubber and plastic brittle.
On mine I'm having to go through all those little things replacing them for ageing. Still got a bunch of minor things like that to replace next week, I've just done all the major things like brakes, steering arms, fuel pumps, etc.
For a more flexible response, better low end with the bonus of a top end increase the DOHC 16v engine is meant for it. With the SOHC you're looking at engineering compromises, they have great outputs in their class but it's up in mid range due to mechanical layout. Mercedes could've made them more torquey which is what US/Aus manufacturers did with their mid-level passenger market engines but you lose mid-upper range and overall outputs that way, effectively detuning engine potential which Mercedes didn't want. These cars can be used on the autobahn, a local Aus/US four in its class in the mid-80s doesn't have anywhere near the high speed acceleration/cruising characteristics of them.
But to get faster bottom end without losing upper range you can use high tech like the modern engines, variable length intake manifolding, 4v/cyl DOHC, or cubic inches. 2v/cyl engines are always going to be a compromise of valve sizes for more flow = reduced bottom end harmonics, more cam lift or timing overlap = reduced bottom end, it's compromises due to layout.
For a cheaper alternative to a DOHC 16v swap mechanical retuning is the better option than messing around with spark. How about looking into a simple head port/polish (stock valves). A tow-grind aftermarket camshaft. Exhausting, particularly tubular primaries. Weigh up what you're going to spend in total before you start though because just swapping out for a 16v engine might be cheaper and remains better.
On mine I'm having to go through all those little things replacing them for ageing. Still got a bunch of minor things like that to replace next week, I've just done all the major things like brakes, steering arms, fuel pumps, etc.
For a more flexible response, better low end with the bonus of a top end increase the DOHC 16v engine is meant for it. With the SOHC you're looking at engineering compromises, they have great outputs in their class but it's up in mid range due to mechanical layout. Mercedes could've made them more torquey which is what US/Aus manufacturers did with their mid-level passenger market engines but you lose mid-upper range and overall outputs that way, effectively detuning engine potential which Mercedes didn't want. These cars can be used on the autobahn, a local Aus/US four in its class in the mid-80s doesn't have anywhere near the high speed acceleration/cruising characteristics of them.
But to get faster bottom end without losing upper range you can use high tech like the modern engines, variable length intake manifolding, 4v/cyl DOHC, or cubic inches. 2v/cyl engines are always going to be a compromise of valve sizes for more flow = reduced bottom end harmonics, more cam lift or timing overlap = reduced bottom end, it's compromises due to layout.
For a cheaper alternative to a DOHC 16v swap mechanical retuning is the better option than messing around with spark. How about looking into a simple head port/polish (stock valves). A tow-grind aftermarket camshaft. Exhausting, particularly tubular primaries. Weigh up what you're going to spend in total before you start though because just swapping out for a 16v engine might be cheaper and remains better.
11-07-2012, 02:54 PM
#30
Member
Thread Starter
well i just replaced both engine mounts, the tranny mount, fuel filter, oil filter, oil change, hazard switch, coolant level sensor, drive belt, and intake manifold gasket. when i put the manifold back on and connected the throttle linkage back up i adjusted it a bit and it now lights the tires up in second gear with a little kick down and im running decent porteza tires. i also soaked the injectors in rubbing alcohol and cleaned the manifold out with carb cleaner. it now has more get up and go and no hesitation. my seat of the pants meter went off the scale the first time i fired it up. i wasnt expecting it to get up and go like it did and layed a 15 foot 11 mark on my street. i also trimmed the cold air intake down about 3/4" on the curved side next to the radiator and it made a noticeable difference as well.
11-12-2012, 02:52 AM
#31
Really? I've been considering cutting the air intake curved side on mine for a bit extra but was thinking it might just be superfluous. You got noticeable response? Coolies, I might do it. Got a nice K&N filter drop in coming next week or so, be good to feed it.
Well, sounds like you're just looking for some classy, minor improvements to help the enjoyment along. Look up some German based tune shops for aftermarket camshaft grinds, for around 450 euro you should swap out for a sportier grind. Between that and some port and polishing you maybe really happy with it. That's basically what's in store for my 2.6, I was going to go the expense of a 3.0 swap but having listened to some that've done the swap it seems you can get similar enjoyment from a warmed over 2.6 which is much cheaper for me. Mostly it's about replacing all the aged parts for new to get back that factory release performance, which is actually very good throughout the range. An engine swap is only a must do if you've got a 180 with a 2.0 or 1.8, in which case better just buy a 190.
Well, sounds like you're just looking for some classy, minor improvements to help the enjoyment along. Look up some German based tune shops for aftermarket camshaft grinds, for around 450 euro you should swap out for a sportier grind. Between that and some port and polishing you maybe really happy with it. That's basically what's in store for my 2.6, I was going to go the expense of a 3.0 swap but having listened to some that've done the swap it seems you can get similar enjoyment from a warmed over 2.6 which is much cheaper for me. Mostly it's about replacing all the aged parts for new to get back that factory release performance, which is actually very good throughout the range. An engine swap is only a must do if you've got a 180 with a 2.0 or 1.8, in which case better just buy a 190.
11-12-2012, 03:42 AM
#32
Member
Thread Starter
it was noticeable. just know that once you cut it down you can hear the air moving in at that point (which you could not before) its not loud unless you really put your foot down and even then its not a hiss its more of a rumble. the engine seems like it revs quicker now too. Next on my to do list is struts, strut mounts, alternator, fan clutch, water pump, thermostat, and tensioner pulley and shock.
