325i cab power increase !!

due to financially trying times , i have had pass the ownership of my cab over to my old man . now its not quite as upsetting as it could be as he's got the money to spend on it and will get it finished .

 back on topic ,,  he wants to give it a bit more grunt once he/we sort the suspension out (horrible understeer oversteer type of feeling) . i wont be doing any major mechanical mods for him as he just wants a little bit more ooomph . it allready takes out stage 1 rs turbo's but it still feels slow to me

 i was just wondering who has modded their 2.5s and what sort of power output they have acheived ? i allready fitted scorpion stainless and filter . it has the 325 motorsport lump in it and im not sure if theres any difference at all from normall 2.5s?? 

tbh i got bored with it lacking in the power department so i look forward to trying to get it quicker with someone elses money .

opinions experiences welcome

taa muchly

Hmmm, now for the proper answer.

The ported throttle body will give you far greater pulling power throughout the rev range and it is noticable.

The chip is also VERY noticable, (ask forum mod nigel, i did his)

Porting the head is worth 2-4hp (if you manage to make power)

I had a 3 grand head on my car and trust me, there are little gains in the head porting, in 1991 CCC gave an M20 head to Dave Vizzard and in 2 weeks of extensive work he got 2hp !!!

The m20 and m30 heads are very good standard.

Now for the afm.

Yes, get rid of this and fit a map and you will be happy, this needs aftermarket ecu like emerald, vtech, etc etc.

Throttle boddies like dbillas are good but cost 1800 quid and will make many problems setting them up.

Get throttle body, chip and decent air filter and you wont regret it. 

I'd use a Schrick cam, the increased size throttle body, have a MAF fitted instead of the AFM then you'll have to use stand alone management to run the fuelling, that last option won't be cheap but i've seen it in a car and felt it, sounds wicked to!

Best to have it mapped on a rolling road by a reputable firm if you're after then best gains, if you want to move the power band up the rev range then fit an aftermarket exhaust.

chippeduk wrote: Hmmm, now for the proper answer. The ported throttle body will give you far greater pulling power throughout the rev range and it is noticable. Porting the head is worth 2-4hp (if you manage to make power) I had a 3 grand head The m20 and m30 heads are very good standard.

With respect, that thing about the TB is a load of cobblers. The engine wants to fill it's cylinders all the time that it's running. The throttle attenuates the flow so that they only partially fill and the engine doesn't rev it's big-ends off all the time.

Now, make the TB slightly better at flowing gas and all you'll get it slightly better power for a given throttle opening, but the power at a given engine speed it likely to be exactly the same as it ever was.

Only when the TB becomes a restriction in it's own right, at wide open throttle, will you notice a gain.

Also, the TB is bolted to a sand cast aluminium inlet manifold which is rough as a bears behind and doesn't exactly aid gas flow.

I'll admit that different heads respond in different ways to porting. However, if you paid £3k, then you were stiched up like a kipper! For around £700 you can get a reputable company to port a 16v head to race spec (none of this stage 1,2 and 3 <rap) so a 12v shouldn't be any more expensive.

Again though, the specific power output of these engines isn't anything to write home about and that's because they were mass produced with no particular attention being paid to the finish of the relevant bits.

hehehehe.

I know all about race engines and builds.

The FACT is there are not worth the high costs when modding the M20 head.

If dave walker could only get 2hp from this head by porting and flowing then you tell me someone who can get much more.

Of course this does not relate to all engines, My escort cossie saw 14hp from head work (not cams) so i know how they work but this thread was about the m20 head.

Anyway, back to the throttle body.

You will definately see a gain throughout with the ported throttle body.

Having said that, the gains felt when driving are more spectacular.

I am yet to find someone who has done this and said they didnt notice the difference, if you know of anyone please point them here to explain. 

chippeduk wrote: Mind you, i`m probably a joker who is making a wild guess at all these claims :D

Well we didn't want to say anything

Only kidding, but you're right about that level of modding, just not worth it on the M20 IMO, if i was at a stage where i needed polishing and head porting then it'd have to be on a multivalve engine to make it worth my while.

nice !!

evo motor i presume ? 

tbh if performance was really the biggest issue with the car  we wouldnt have bought it , but we do feel its a little sluggish hence the post .

i think its probably gna end up with a cam and a chip as long as it keeps its driveability we,l be happy . if it was a real performance issue i,d be looking at doing a low comp turbo conversion or the twin supercharged jag v8 but it really isnt worth it .  i think i have spoilt myself by driving  really fast cars like my saff and now it allways feels like everything else is positivly slow . 

 as for high power e30's , one question ,,,,  what diff , g box would you use ? surely the e30 stuff wouldnt handle it too well ?