1.6L to 2.5L

[ipwnyou 0]

Someone is offering me an upgrade of my engine - from my 1.6L Manual to a 2.5 - keeping the gearbox so staying manual. They have also offered to do the change. I think its from an M20.

They havent given me exact prices yet, but it'll come in under a grand.

I dont know a hell of alot about engines, but its obvious that 2.5 - 1.6 = 0.9L of extra power - but how much of a difference would it make? They also tell me that after a reconditioning (for extra, of course) it would perform around a 2.7 - does that sound right?

Any input would be great.

[E30stz 0]

just curious anyone - how much is the weight difference between these different engines. How much of a gain do you need before you start thinking about changing the suspension. I spose it cant be more than a heavy person but then again it is to the front of the car and isnt evenly dispersed.

Next problem is you cant use a 316 gearbox with a 325 unfortunately. You will need an M20 gearbox unfortunately.

Horsepower jump is literally 70 horsepower. So your nearly doubling your output.

Details about the two cars

Model/engine/cylinders/horsepower/topspeed/year.

316i M40 4 cylinder 100 HP 182 km/h 1988 - 1991

325i M20 6 cylinder 170 HP 220 km/h 1985 - 1991

top speed could differ seeing as your car wont be a factory assembled 325.

Edited October 3, 2005 by E30stz

[ipwnyou 0]

Sweet info man - I'll query them about the gearbox - because I dont want an auto, even if that means staying 1.6

Would be interested about the suspension also.

[Carl 3]

There's several things that you need to consider if you're going to dump the 2.5 engine into your 316.

As pointed out above, the gearboxes will NOT mate up, only a 325 g/box will work with the 325 engine so you'll need a 325 g/box and driveshaft.

You will have to change over the wiring loom and ECU etc.

You will have to change the rear differential unless you want to have nice close gearing with no economy.

You will probably need to upgrade your rear brakes as they will be drums no doubt.

You'll probably have to upgrade your suspension if you haven't already.

You'll need certification.

[E30stz 0]

as much as it doesnt seem worth it, going from 100 - 170 horsepower is well worth it... but maybe you'd be better buying a 325 as its probably going to end up costing as much as buying a new one.

[ipwnyou 0]

Thanks for the input Carl - I'll raise all of these questions with the mechanic. I have a few questions, though:

As pointed out above, the gearboxes will NOT mate up, only a 325 g/box will work with the 325 engine so you'll need a 325 g/box and driveshaft: Will these fit in my E30 from the 325?

You will have to change over the wiring loom and ECU etc.:

Figured that - They offered to also do this.

You will have to change the rear differential unless you want to have nice close gearing with no economy.: Also, is this able to be taken from the 325?

You will probably need to upgrade your rear brakes as they will be drums no doubt.

Yeah, Drums, and I was considering getting that changed anyway. Not sure of the cost, though, as I woudlnt imagine it to be that cheap...

You'll probably have to upgrade your suspension if you haven't already.:

Suspension is aftermarket, but im not 100% what it is - I would have to take a closer look.

You'll need certification.

Not sure how hard this is to get...

[ipwnyou 0]

My friend acutally has a 325 that they are wrecking, as the body is just too crap to do anything with anymore. Thats why im asking - so if most of the parts are compatable between the two bodies then cost shouldnt be too much of an issue, just time.

[Carl 3]

All the 325 parts will go onto your 316 no probs, that's the beauty of the E30 and BMW engineering, as for the cert that's just a formality I believe but an additional cost at any rate.

Edited October 3, 2005 by ///Carl

[E30stz 0]

I assume diffs dont matter based upon gearbox being manual / auto ?

[Carl 3]

The diffs do matter, the 316 will still have a high ratio diff even for the manual, will be a 4.11 most likely which is almost acceptable with the 325, get Gus's 3.73 if you do it.

[ipwnyou 0]

Sweet - sounding better and better. I'll be finding out in a day how much for the conversion + the rest of the parts. Is there anyone else that does that kind of thing, so I can compare prices?

Also, what does the Cert cost?

[E30stz 0]

no doubt people on here will have the parts you require. You should have a go @ the LSD on trademe

Edited October 3, 2005 by E30stz

[ipwnyou 0]

LSD?

[E30stz 0]

Limited Slip Differential - better ratio gearbox and means both wheels spin at once.

A highly sort after part - http://www.trademe.co.nz/Trade-Me-Motors/C...on-36824327.htm

[ipwnyou 0]

Holy crap...it'd work without one of them, right? That bastard isnt cheap.

[Gus 5]

ideal if you have a complete donor car....you need a 5 spd box, but being manual already its good cos the whole pedal box, shift lever thing is the same. so you literally need just the box

its very worth it, the 325i is not a fast car, but its reasonably quick. dont forget the extra torque. its fun. if the donor car is an auto, check the diff before you whack it in. anything higher than a 3.91 would prob be a little high for 5 spd. (but usable)

there plenty of people on here to give advice and help when (not if!) you get stuck

the only prob i could forsee is the plug going to the main car loom...is the donor car a facelift or pre FL? if its facelift i imagine it would be sweet

[ipwnyou 0]

I have a feeling its p/fl - and mine is fl. I'll check that out.

And yeah, WHEN i get stuck is true - im sure ill get pwned a few times before the car is running again. Can anyone here reccomend a garage or know off the top of their head what the cost of the work would be to do something like this? I dont wanna get ripped by the people im getting this 325 off that have offered to do it for me.

[petone 0]

I agree with pretty much what everyone else has said, definatly do the swap. As long as the parts car is there the swap shouldn't be too bad, you'll find there are lots of little bits you'll need like driveshaft, oil cooler etc.

As for diffs, my mate had a 3.91 in his 2.5 and it would out run vtec preludes, but it did have very short gearing, wouldn't want to go any shorter. Lastly what did they say they were going to do to it do get it performing like a 2.7? The 2.7 strokers apparently make around 200hp, your rebuilt 2.5 will only make 170hp.

[ipwnyou 0]

Oh and does anyone just happen to have a 325 or compatable 5speed manual gearbox just lying around, do they?

[ipwnyou 0]

They said if the engine was reconditioned it would perform at the level of a 2.7 litre car. Im not 100% sure what they mean by reconditioned, like as in what it would include, but i probably wouldnt worry for now.

[E30stz 0]

if its pre-fl going into facelift wont you need a new exhaust or take the exhaust over in the conversion as well ?

[ipwnyou 0]

I was just about to ask about that - I have a custom exaust setup at the moment - I'll probably have to ditch that or get it modified again.

[ipwnyou 0]

Just got some info on the car - its a 525i 2.5L M20 E34 1989. Is that bad?

Edited October 4, 2005 by ipwnyou

[petone 0]

Yip.

You wont be able to use the rear disc brakes. Driveshaft won't fit, neither will the bigger front struts (Not a big deal but they are stronger). I'm not sure how the loom and ecu will work either. Engine mounts and oil pan might also cause problems. Other people on here iwll be able to tell you for sure about the loom, mounts and oil pan.

Basically unless you can find a 325i parts car it going to cost you quite a bit more.

[ipwnyou 0]

Well it looks like quite a few of the parts I need are already available from some of the members here that have PM'ed me - thanks guys. I'll let you know how it goes on the conversion. Should be interesting...and expensive!