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M88/3 strip...

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Dan101smith
Posts: 90
Joined: Sat Apr 05, 2014 5:33 pm
Location: Herts

M88/3 strip...

Post by Dan101smith » Tue Jan 10, 2017 7:00 pm

...and hopefully a rebuild too!

Thought I'd make a thread, mostly so I'll have something to refer back to, but also for any creative input the collective may have.

Brace yourselves - this is E28 related, although the engine did start life in an M635.

The background is that this engine lives in my E28 race car. It was bought to replace an M30 that I spent loads of money tuning for very little gain.

As part of the installation I managed to do a deal on a nice big carbon airbox, and so in order to go Alpha-N I went with an Omex 710 ECU. During the mapping stage, the guys heard a feint knocking from the bottom end while on the dyno. Cue some poking around, and the upshot was this:

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As rod bearings go, not the prettiest I've seen.

Cue many months of ignoring it in the hope it'd fix itself (it didn't) until last week I finally pulled my finger out, pulled the engine out and tore into it.

This:

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became this:

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which after only a mild amount of swearing became this:

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Now, armed with the TIS, a cup of tea and a modest selection of tools, I hit a couple of hurdles along the way that I wasn't sure how to proceed with. The first one was the exhaust cam sprocket. The TIS states for both cams that you simply remove the bolts to remove the sprockets. It wasn't quite as simple as that, as this pic should show:

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Without an obvious, non-intrusive way to get a socket on them I decided that the safest approach would be to cut the chain, which allowed for the intake cam to be removed. The exhaust cam is still in-situ until I work out (read: someone gives me a steer on) the correct approach to cleaning that up. It didn't seem to cause any issues in removing the head, so I was happy to work around it for now. As I'll be replacing the chain, sacrificing the one fitted wasn't a problem either.

With everything separated I was able to take a look at the pistons and valves, to see how they've stood up to [insert unknown-but-sold-as-140k mileage here] miles. Even I don't find the following pictures hugely thrilling, but in the interests of completeness I'll add them anyway:

Cylinder 1:

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Cylinder 2:

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Cylinder 3:

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Cylinder 4:

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Cylinder 5:

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Where it may border on becoming moderately interesting is with Cylinder 6:

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5 pistons showing identical colouring, one visibly different. Answers on a postcard please...

So that brings us up to where we stand today. Given the "unknown" status of the engine (and also that I *may* have set it on fire at one point) my plan is to take the block in to a local engineering company and ask them to do any and every check on it that they can, to verify that it is sound and a viable base from which to continue.

I'm hopeful that it is, and so that will then take me down the rabbit hole of what to do to it during the rebuild. Everything is fair game at the moment - the biggest issues being the relative lack of tuning knowledge around the M88 and the scarcity of performance parts this side of the pond. What seems to work in my favour is that the M88 is mostly six quarters of an S14B23, and so there is parts overlap between them. From some reading up I've done on the common S14 tuning routes, it seems the popular path is to go for bigger intake valves, lumpier cams, up the compression ratio and ditch the AFM. All good theory assuming it translates from 4 to 6 cylinders. Where I'm struggling (did I mention I'm not an engine guru?) is in choosing the right spec for all these parts such that they will complement each other and give me a good, solid race engine. I'm not after crazy power, but somewhere over 320bhp would be nice.

As an aside, while the engine is out I'm looking to take this opportunity to make a couple of other changes to the car too - I've got an electric PAS pump to fit (potentially the fastest a Merc A Class PAS pump will ever go!), I've ordered an oil filter housing delete plate that'll allow me to run an inline filter and tidy up the plumbing somewhat, and I will finally fit the nicely powder coated, reinforced front subframe I've been tripping over for months.

So, all comments, ideas and positive feedback welcome! I know we have a geographically diverse membership on here, but I'm sure wherever you are you'll be able to hear my wallet weep.

If you made it this far you've earned yourself a cup of tea. Me? I'm off for a little sob...

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Brucey
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Re: M88/3 strip...

Post by Brucey » Tue Jan 10, 2017 7:20 pm

if it were not a race engine and money were tight, I'd be suggesting that you check the crank, check the piston ring end gaps, bore wear, little ends, etc and if they are OK, sling it back together with new shells and new timing chain parts. This will avoid much of the expense of a full rebuild.

But for a race engine, that probably isn't the right thing to do. Most S14 tuning does translate, but I'd argue that 320bhp is a very modest figure to aim for, in a race motor.

I'm not sure what you are hoping to achieve by using a remote filter, but do note that a simple blanking plate won't work on every M30/M88 motor, because in some versions one of the openings in the block is a return passage for oil that burps past a pressure relief valve or something.

On a race motor, I'd suggest that you think about either

a) fitting a dry sump kit (which can allow you to fit a shallower oil pan and to lower the whole motor) or
b) fit an accusump kit.

In any event fitting a crank scraper/baffle plate is a good idea, else the motor can run out of oil pressure on long left-handers (which could be how your rod bearings got to be the way they are.... :roll: )

BTW your hand will doubtless be stayed somewhat by the fact that no-one has a bottomless wallet, but the other thing that is worth considering is that any race series you intend to run in has a whole list of things that you can and cannot do to your engine. You may find that a 'nice to have' item that doesn't actually give you much power increase has the effect of making it so that you can't run in certain race classes or race series, so choose carefully.

cheers
~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

GazM3
Bigcoupe supporter
Posts: 1677
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Location: Melbourne, Australia

Re: M88/3 strip...

Post by GazM3 » Tue Jan 10, 2017 9:18 pm

I love a good engine story. As brucy said the accusump is a nice insurance policy for racing.

As far as the engine side is compression, cam and capacity are king. There is also power left on the table if u can rev the engine a little more. An upgraded crank hub is pretty well the only major thing limiting the rpm to 7000 or so. Upgrade this and u can spin it up towards and even beyond 8000.

A small lift in compression can be gained by using a thinner head gasket and you probably will need to either slot the cam wheels to make them adjustable and/or get a machinist to carefully enlarge the valve pockets on the pistons.

On the capacity side I'd investigate using the m30b35 (86mm) crankshaft which will give a nice capacity lift to 3.65ltr (from 3.45ltr) for not much cash. Upgraded fasteners (arp) will be mandatory.

You are on the right track going for a standalone computer. Often people spend a fortune on doing thier hotter engine and compromise it majorly using the std computer. One that uses no airflow metering will give freedom on the intake and one that runs on a wideband sensor will be easy to tune and give a nice bonus of improved fuel use. Also if u convert to sequential fuel injection and individual coils u will be able to run bigger cams and still keep it drivable.

On the subject of cams most are designed for the s38 so the tunnels of the m88 need some machining which is no big deal but still needs to be done. The relationship with cams and compression is such that the bigger u go with the cam the more compression it needs to make it efficient. More compression also has a calming effects on larger cams.

If going for a nice big but streetable cam you could easily run 12:1 comp on Ron 98 fuel where if u were using the factory cams you would be limited to around 11:1. If going more than 11:1 you would need to run aftermarket Pistons to achieve it.



There is no doubt with a moderatly crammed up m88/3 on high compression (11.5-12.0:1 depending on how big the cam is), with a bit of a capacity lift could make over 400bhp with keeping rpm below 8000. Even with very mild cams (say factory s38b38) with bigger crank, standalone management, 11:1 and 7200rpm will make over 350bhp and have much more low down torque than the factory engine.

The good news is that the aftermarket components required are actually cheaper than the factory ones.

Good luck.
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Dan101smith
Posts: 90
Joined: Sat Apr 05, 2014 5:33 pm
Location: Herts

Re: M88/3 strip...

Post by Dan101smith » Wed Jan 25, 2017 9:01 pm

Brucey wrote: I'm not sure what you are hoping to achieve by using a remote filter, but do note that a simple blanking plate won't work on every M30/M88 motor, because in some versions one of the openings in the block is a return passage for oil that burps past a pressure relief valve or something.
This is what's on the block:

Image

I've never studied an M30 version, but I assume this is safe for the VAC plate.

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ericono
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Posts: 486
Joined: Fri Mar 23, 2007 1:51 am
Location: Spartanburg, SC

Re: M88/3 strip...

Post by ericono » Fri May 18, 2018 1:55 am

Hey Dan,

Any progress on this? Would love to hear what's going on and see more pictures.

Thanks,

Eric
'85 M635, '00 528iT, '98 Z3

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