Injector/Intake manifold design. - PeachParts Mercedes-Benz Forum

Pagz · #1 12-17-2010, 04:02 PM

Guys,
It would seem the root of all my engine sealing troubles may revolve around my intake/injector setup,or more to the point...the bore wash it could be causing.

Possible reasons to believe intake and injector setup is causing bore wash:

-The 560cc injectors(OE is 280cc) are mounted in the stock location close to the valves,they are a split spray mitsi evo 7 injector and are mounted in the approx same location at the same fuel pressure on a evo7,however im not sure where the spray pattern actually hits,ideally the back of the valve or so i have read. it is possible that these are not far enough back to atomize.

-Very short intake runners that are a larger diameter than stock,so i would imagine low air velocity/cylinder filling at low rpm would not help the fuel situation.

-Tuner noted quite a lot of fuel is needed to hold a smooth idle and on cranking!!

-Small amount of black smoke throughout RPM under WOT,even though mixtures look good...hmmm but dont oxy sensors read oxy,they dont read fuel left over on the bore???.

-Engine hesitates once only under boost after idling/cruising in the lower rpm band for a few minutes,(suspect fuel buildup around rings etc)

-Every engine build has ended with fuel in the oil,never any broken rings.

Are these good enough reasons to believe we have fuel ending up around the rings?...if anyone has any experience with bore wash and it wasn't a failed injector please share!.

My plan if i go through with it is to remake my intake plenum with longer runners to allow a secondary injector setup,we would use stock injectors with an additional set of say 300cc up stream,has anyone here ran this sort of setup and were there implications around bringing the second set on smoothly?. other questions are where to locate the secondary injector from valves and how long to make the runners!??.

Its a fairly big undertaking to accomplish this as i need to change nearly everything even the ECU needs changing as i will need 8 injector outputs,new fuel rails,all plumbing on that side not to mention many hours more on the gold plated dyno.

I guess the big question is do you guys think there's enough evidence there to warrant doing all this work?...what if it ends back where i am now?...if mitsi's can run 400hp effortlessly im sure the M111 can...geeez why must it be so hard^^.

Cheers,
Paul

JayRash · #2 12-17-2010, 04:35 PM

It can very much be bore wash, and it sure is worst at idle when little fuel is usually needed and the rest will just clean the cyl walls dry causing the rings to wear out.

what u can try is plug new places for the inj further back and just close the old ones and run the car few km and then check if there is alot of fuel in the runners and around the valves. if its distance you need for the fuel to atomize then try this and see. if it works out it will save u lots on total make over of the intake and fuel rails / ecu.

300EVIL · #3 12-18-2010, 02:44 AM

Before you change position. I'd try injectors with different spray patterns. Rochester injectors offer a very unique spray pattern that may correct your possible combustion issue. There are many years of engineering involved in injector positioning and design but I believe your problem can be corrected without too much modification.

Pagz · #4 12-19-2010, 06:30 PM

Thanks guys, both those are options but im unwilling to try them,moving the injectors on my plenum is not feasible and requires heaps of changes,buying more injectors then spending more hours on the dyno is hard work also(huge cost and time and by the sounds i still need to rebuild this engine)...one option im seriously considering is parting out the engine bay and buying a cheap C36 car to transplant onto my manual gearbox...the only problem i can see is getting the stock ECU to work with the security and without the auto's ECU....

Does anyone here know the complications around not having the auto ECU?...do we need to fudge some inputs/outputs?...im in the dark when it comes to autos but its a mercedes and at a guess the ECU probably reduces power between gears to help smoothness??....

At the end of the day if the engine behaves normally without the auto ECU this swap will be incredibly easy.

MagnumPI · #5 12-19-2010, 09:11 PM

Quote:

Originally Posted by Pagz

Thanks guys, both those are options but im unwilling to try them,moving the injectors on my plenum is not feasible and requires heaps of changes,buying more injectors then spending more hours on the dyno is hard work also(huge cost and time and by the sounds i still need to rebuild this engine)...one option im seriously considering is parting out the engine bay and buying a cheap C36 car to transplant onto my manual gearbox...the only problem i can see is getting the stock ECU to work with the security and without the auto's ECU....

Does anyone here know the complications around not having the auto ECU?...do we need to fudge some inputs/outputs?...im in the dark when it comes to autos but its a mercedes and at a guess the ECU probably reduces power between gears to help smoothness??....

At the end of the day if the engine behaves normally without the auto ECU this swap will be incredibly easy.

I believe the very early C36's didn't have the auto transmission ecu trouble, still the old style.
If you do part it out, I'd be interested in the turbo manifold, and flywheel.

JayRash · #6 12-20-2010, 01:31 AM

the 4 speed 36s dont have ECU for the auto but there is a terminal used by the ecu to reduce timing on shiftup from 1st to 2nd and that should not be too hard to fool. It connects to a sensor called an overload switch.

Pagz · #7 12-22-2010, 01:55 PM

Thanks guys,
So the 94/95 maybe early 96 C36 would be the way to go for sure...i could install the C36's trigger onto my flywheel and reuse that.
Jay,while on the hunt for C36 info iv seen those vids of your hill climbs,plenty of wheel spin you must have been moving

,is it normal in your country to make people move out of your way in any lane?^^

MagnumPI,pm sent.

JayRash · #8 12-22-2010, 03:42 PM

Quote:

Originally Posted by Pagz

Thanks guys,
So the 94/95 maybe early 96 C36 would be the way to go for sure...i could install the C36's trigger onto my flywheel and reuse that.
Jay,while on the hunt for C36 info iv seen those vids of your hill climbs,plenty of wheel spin you must have been moving

,is it normal in your country to make people move out of your way in any lane?^^

MagnumPI,pm sent.

LOL, i know i shouldn't have :$
but yeah u can impose on them to move over, and yes the 36 has alot of spin, i have tried everything, new everything including R888 semi slicks as daily driver wheels, the tarmac we have is low grip, in most places.

and this is a heavy 1700kg car. I like it thou, and if this engine is put in a W201 manual it should make a sweet ride.

i do think that C36 before 96 have the old three point trigger. Not very sure info here, so use with care.

BAD300 · #9 12-22-2010, 04:12 PM

Quote:

Originally Posted by 300EVIL

Before you change position. I'd try injectors with different spray patterns. Rochester injectors offer a very unique spray pattern that may correct your possible combustion issue. There are many years of engineering involved in injector positioning and design but I believe your problem can be corrected without too much modification.

Interesting! I am getting a custom made Boxy Plenum myself with short runners, velocity stacks etc (for a reason). Are you using a Plenum or just a cut-down inlet mani? You need the Plenum to cause the high volume of air & correct velocity issues (as far as content is concerned).

One thing I feel a need to add here for benefit of anyone mucking around with IM's etc: a poorly-built EM can cause both turbo heat/turbulence probs as well as engine damage. Better believe it! As for the IM. Enrichment probs are very likely due to poor design/fabrication. One area @ least to consider, as OP has touched on

I would have thought this suggestion by 300EVIL both viable & cost effective. I'm pretty sure my workshop is using the Rochy Injectors also. Maybe they are worth a try? Easy mod to do & you can sell off the other set to get some $$'s back surely?......know what I'd be doing.

I know this is concerning EM's but, I personally witnessed a very poorly designed turbo manifold ruin an engine. There was so much turbulence caused by a dodgy 'merge collector' fabricated. Instead of each runner meeting @ a given central point. They pointed @ each other directly, prior to merging down toward the cylinder head ports

P.S.

Quote:

Originally Posted by JayRash

........and yes the 36 has alot of spin, i have tried everything, new everything including R888 semi slicks as daily driver wheels, the tarmac we have is low grip, in most places.

Jay, at least you aren't going to break any of the running gear with wheel spin. It's the gripping that will break a diff gear tooth/spline, housing, yoke, u-joint....whatever else takes up the slack

Interestingly, when I choose the tyres for my beast on the 18's, I naturally want soft compound tyres, especially for wet driving but, if they slip, this equates to a softer pull on the drive chain & much less likelihood of breaking teeth

Pagz · #10 12-22-2010, 09:25 PM

Quote:

Originally Posted by JayRash

LOL, i know i shouldn't have :$
but yeah u can impose on them to move over, and yes the 36 has alot of spin, i have tried everything, new everything including R888 semi slicks as daily driver wheels, the tarmac we have is low grip, in most places.

and this is a heavy 1700kg car. I like it thou, and if this engine is put in a W201 manual it should make a sweet ride.

i do think that C36 before 96 have the old three point trigger. Not very sure info here, so use with care.

Impose,maybe not quite the word i would have used^^LOL
Must be time you got an lsd of sorts,as tricky as it may be to obtain and fit one i think you definitly need it!
Either way with the trigger im sure we can make it work,the bits that might be alittle more tricky is the ASR(if i want to make it work again) and things like AC etc which require compensation,im not sure how the ECU knows when its switched on.

MAG58 · #11 12-22-2010, 11:19 PM

Pagz, if the early C36 is like the old merc's (W201/W124's) It's a piece of cake to bypass the trans. There is a 5 wire plug that goes into the shifter: Two small wires go to the backup light on the shifter. The other three go to a relay: The large and small wire's that are crimped together go on one side with the big single wire on the other. Then run a switch to either your clutch pedal or a switch on the dash (what I did). Pressing the switch triggers the relay and the car thinks it's in N or P which allows it to start, and has the N/P rev-limiter. Once's it's started you can take your finger off the switch and she'll run like she's in Drive. So far 15k trouble free miles on my setup that way. Also serves to be a bit of a theft deterrent since my switch is under my dash, so only I know how to start it

.

As far as the LSD thing goes, apparently the Nissan S13 backplate is close to our merc's and the GTR pumpkin can be put in with it. Just get some half shafts and be done with it, or use ASD shafts and have some adapters made. I'll be trying this soon when my 201 goes FI.

400Eric · #12 12-23-2010, 01:01 AM

Quote:

Originally Posted by JayRash

the 4 speed 36s dont have ECU for the auto but there is a terminal used by the ecu to reduce timing on shiftup from 1st to 2nd and that should not be too hard to fool. It connects to a sensor called an overload switch.

Jay, I had an ongoing thread on this very topic over on 500Ecstacy and none of us were able to come up with a viable solution. If you have one I would love to hear it. I've already tried hooking a "dummy" one up in place of the original, much like how I did the CTS but it didn't work.
Regards, Eric

BAD300 · #13 12-23-2010, 01:35 AM

Quote:

Originally Posted by Pagz

Must be time you got an lsd of sorts,as tricky as it may be to obtain and fit one i think you definitly need it!

There are LSD's a plenty in Jay's neck of the woods

I enquired about one not long back. Cheap too. Cost us far far more to import one down here where there are absolutely none. Bout six times as much for the 2.3L 16V Cosworth LSD. Most are shagged due to high mileage & need new clutch plates etc anyhow unless you use a block

Quote:

Originally Posted by MAG58

......the Nissan S13 backplate is close to our merc's and the GTR pumpkin can be put in with it. Just get some half shafts and be done with it, or use ASD shafts and have some adapters made

I may be looking into this up ahead as I'm not interested in rebuilding an older, 24v model w124 LSD & importing a C'Worth diff is out of the Q, at least for now

JayRash · #14 12-23-2010, 02:01 AM

@ BAD: Yeah we have plenty here and cheap too, an ASD Diff is abt 150USD now, an old 2.3 LSD n more than 200+.
Its time that is the issue.

@PAGZ, yeah i know i need an LSD, its probably the best improvement this car badly needs. especially now that the TOYO R888 have doubled in price. from the usual USD800/ 4 to 1500!!!!!.

and all they can do is some 6000miles at best.

@Eric, from what i know your boxes have 2 of those annoying switches. and they aint cheap either.well i am sure they need to be under some pressure for the ecu to read proper, and they need to pass the ecu checkup everytime it starts, so it wont be as easy as i made it sound. Prolly some small electronic board is needed since all what the ECU reads is resistances at each state. so the board should mimic the resistance when the solenoid is activated on start check up. and then the normal resistance say in drive on idle.

this is all assumption and you know what i say abt that

post the link here so i can read it all plz.

400Eric · #15 12-23-2010, 05:51 AM

I would have already posted a link in my post above but the site is down and has been for some time. I'm sure it will be back though and I'll link it then. Thanks for showing an interest!

The only boxes that have 2 of those annoying switches are the ones that are behind the M120 V12s. The second switch is to retard the timing on the 2-3 shift. The rest of the boxes, even the 4.2 and 5.0 M119's boxes, have only one switch which retards the timing on the 1-2 shift.
Regards, Eric