M42 Bore out help

Post Sun Aug 02, 2009 10:42 pm

Hi guys, i have a spare engine that im going to build up with as much tuned as i can, i know theres not much i can do, but i was wondering what costs are involved in the bore.

I know i need new pistons and rings, but can i get away with no new conrods, no headwork, original injectors and without a remap.

Thanks
Mark

Post Mon Aug 03, 2009 12:04 am

So increasing engine capacity without increasing fuel / air ratio, sounds like a plan for wasting money.

Seriously, what do you plan to achieve by just increasing the bore capacity?

Post Mon Aug 03, 2009 2:48 pm

This is why im asking for help, would the standard airflow meter and injectors not adjust themselves to accomodate for the extra capacity

Post Mon Aug 03, 2009 4:03 pm

Injectors have a set flow rate so you'd require a set of injectors which flow a higher amount of fuel. The standard fuel pressure provided by the pump is 3.5 bar, you'll find most injectors' flow rates are specified at 3.5 bar any way so you wont need to go fafing about with chaning pressures etc.

As for the amount extra you'd need I'm not sure but I'll PM you the email of some one who can help. Obviously you'll need to have some figures or its darts in the dark

Post Mon Aug 03, 2009 4:23 pm

Sparkysparks wrote:would the standard airflow meter and injectors not adjust themselves to accomodate for the extra capacity

Sparky, so long as we are not talking about a substantial increase in engine capacity (and that you keep your current injectors) then you should be alright with the standard ECU. The slight increase in air flow (at a given value of RPM) past the airflow meter will result in increased injector duration (more fuel) since the ECU will be "looking" to a higher air flow (load) spot on the fuel map.

Where the problem comes in is that (in the event of a major rebore or stroking the engine) the ECU will be looking to areas of the fuel map for its injector and ignition data that were never mapped during the engines previous life, causing you a lot of grief.

Also, anything that dramatically changes the volumetric efficiency of your engine (that effectively changes your engines torque curve) such as changing cams and/or manifolds etc should be accompanied by a remap of the ECU.

In the event that your "tuning" efforts reach the point where your engine requires bigger injectors, your ECU will have to be remapped.

BTW: Is that an R5 I spy in your sig pic?

Post Mon Aug 03, 2009 8:38 pm

Thanks for the help guys,

Whats the maximum bore, i thought it could go up to a maximum of 2.1?

Geoffbob it is an r5, and its in pieces atm, ill wait till thats built untill i take the beemer apart

Post Mon Aug 03, 2009 9:09 pm

You cant just bore the block out to get 2.1 you will need to get a M47 diesel crank and different pistons to make it work. think the maxn any ones ever bored a M42 block out to is 86mm but if your not carful you could end up getting hot spots and melting pistons as the wall between the cylinders is getting very thin at that point

The most you could cheeply do is open it out and possibly fit M44 pistons from a E36 318is 1.9 and if your tanking out the engine to bore it out and youve got the M44 pistons you might as well have just fitted the M44 enigne as a oner.

Sorry to say that if you start messing around with boreing out blocks and new pistons and rings then its going to be expensive.

Post Mon Aug 03, 2009 9:16 pm

Ok so i would need a different crank aswell, ok that changes things,

Post Mon Aug 03, 2009 9:42 pm

well only if you wanted to go to 2.1, guess you could keep the current crank and fit over size pistons but i would have said the cost would out weigh the gains

Post Mon Aug 03, 2009 9:49 pm

Well if im going to do it i may aswell do it as big as i can go.

So what do you all recomend.
bore,
pistons, ring, conrods,
injectors,
crank,
shells,

Would i need to fit liners?

Post Mon Aug 03, 2009 9:49 pm

You could drop the 1.9 internals into the M42, and while you're at it adjust the inlet cam advance by about 5 degrees. I'm sure someone had a motor to a similar spec to this on here once upon a time, running standard management and saw somewhere in the region of 150bhp.

It's said the M42 head flows better than the M44 item too, hence why this combo puts out more than the M44 standard.

Post Mon Aug 03, 2009 9:53 pm

I think the stroker 2.1 IS might be documented somewhere on the zone? Have you tried the search tab?

Post Mon Aug 03, 2009 9:55 pm

n1tr0_9 wrote:I think the stroker 2.1 IS might be documented somewhere on the zone? Have you tried the search tab?

Check the Wiki section or search for tim_s's 2.1 M42 beasty.

Post Tue Aug 04, 2009 9:21 pm

Sparkysparks wrote:Geoffbob it is an r5, and its in pieces atm, ill wait till thats built untill i take the beemer apart

Sparky, if you like R5's, have a look at this

Post Tue Aug 04, 2009 10:12 pm

get on the 24v bus mate, easy power

Post Tue Aug 04, 2009 10:30 pm

Guys i had a look at the wiki section and tim_s e30 thread, looks like its either 1.9 for pointless power or lots of money for something that will still be under 200bhp n/a
Im thinkin i might research the supercharger route

Post Wed Aug 05, 2009 9:37 am

Sparkysparks wrote:Im thinkin i might research the supercharger route

See Appletree's and Rix's builds here, here and here

Appletree is using a Rotrex centrifugal type supercharger and Rix is using an Eaton Roots type supercharger. Be aware of the differences between the different types of superchargers and how they will effect your engines torque curve before you decide which is best for your driving application.

Post Fri Aug 07, 2009 9:21 pm

I had a quick look at those builds, very intense and informative, i prefer the looks of the eaton supercharger, but i like the tidyness of the rotrex. I cant decide on what would work best for me, ill have to do some more research when i can afford to tinker.

I think its safe to say the rebore is off the cards now