325i engine- What bolt on mods REALLY do make a difference?

[StavFC]

As title really. The Wiki page mentions BBTBs and chips, but most info I find via Google is from long long ago.

I know for significant power hikes it's gotta be turbo, but the car's a track car and while I don't need huge increases, a raised rev limit and/or a bit more grunt will genuinely be handy as there's a few occasions where 2nd is too short, but 3rd hasn't the grunt I'd want.

Options-

A basic, straight up, chip. Ethos Motorsports in NI seem to do good ones, and that will raise the rev limit a bit, which will be handy, and HOPEFULLY improve performance too- Anyone ran one and nothing else?

BBTB- Pretty cheap, seems to be reccomended on the wiki page, worth doing on top of the chip?

Ethos also do a M30 AFM and 19lb injector chip, which according to some makes a really big difference, but then I'm not sure and most info is old. Issue here seems to be 19lb injectors and M30 AFMs will have to come from the USA, likely adding another £200 to the cost over a basic chip.
Is it worth it?

Seems induction kits do no good at all, that right? Heard some talk the standard rubber inlet elbow is a little restrictive too? The way the Miller kit below supposedly adds so much, I'd presume the entire intake system is pretty crap, unless it's just the M20 AFM thats the restriction.

Finally, the Miller MAF conversion induction kit thingy- Likely to cost £450+ landed and taxes paid in the UK, and for biggest gains I'd also need the 19lb injectors and BBTB, likely taking cost to best part of 700quid, which is a hell of a lot really, but supposedly 25bhp+ gained from this.
Anyone done this?

TBF just the basic chip for the sake of the raised rev limit will probably do, but I'm more than happy to gain decent amounts of overall engine performance too if its really there and not all BS!

If anyone's done these things and can give a 1st hand account of the differences or anything else, please fire away so I can decide what's what...

Cheers!

[steve_k]

well you seem to have most of the bases covered,

but, before you look into any upgrades, make sure the engine is working as it should, check the dizzy cap, rota arm, plugs, leads, make sure it's in good health, if not, get it how it should be then you can look into performance mods.

also what will the car be used for? street? track? or both?

also, cams? 6 branch manifold? headwork? the list is as long as your wallet is full



don't forget the 2.7/2.8 strokers as well,

[StavFC]

Bases covered yes, but do they REALLY make a worthwhile difference, that's my question.

Ref the other bits- There's no miss or hesitation, so I'd guess I'd gain nothing from changing them.

As I said, it's a track car, and the only main thing I need is either a slightly high rev limit or a bit more grunt to make up for the extra gearchange.

And the car is used often, so I don't want it out of action for headwork/cams/strokers/etc, and tbf the gains for them are so small for the money I'd either go turbo or M52.

Rather not change the manifold as it was enough of a PITA getting the column to clear after the E46 rack swap as it was, never mind with a 6 branced to avoid lol.

[DanThe]

In that case you better start looking for a 24v lump

[jimbom30cab]

It's never going to be an S54 for performance but stuff that really makes a difference

1. BBTB - Very noticable on the M20, better pick up, better sound and slightly better MPG
2. Light flywheel - Again more responsive and feels zippier in the lower gears
3. A good quality chip

If you want to strip the engine down the single most biggest increase is to use a 2.7 crank with your 325i head and inlet. Most noticable is the surge in power from 60mph upwards, it makes a real improvement over standard 2.5

Millar MAF - Yes the gain is noticable BUT you need a proper map, it will NOT work with ANY off the shelf chip - i have tried it. Standard injectors will be fine

M30 AFM and Injectors - yes expect upto 20bhp gain, Rob Ryder prooved this but you need it to be properly mapped, it will not work, might not even run without the right fuel map.

Cam - again an improvement

Pesonally for BHP per pound, i would

1. BBTB
2. Lighten the flywheel
3. Convert to 2.7 (most eta bottom ends are about £200 )
4. Get a 2.7 chip (speedtouch has a clone of mine which was brilliant)

You should be able to do all of that for about £600 if you do the work youself.

[reggid]

I don't think a bbtb or m30afm is is worth anything but throttle response. No real hp gain from my experience. Standard injectors and custom tune was worth it over off off the shelf stuff

If you want stuff that works it's going to cost money e.g rhd itb's kit, cam, head work, btb manifold, stroker, custom tune etc

Lighter flywheel and 3.91 diff will make the car accelerate quicker

[StavFC]

2.7s seem rarer than hens teeth, and as for the other stuff, ill just turbo it or go 24v as that seems better vfm than cams and headwork and itbs.

Like said, the car is used on track a few times a month, so didn't want it off the road for long. Think just a bbtb and chip will do for now, due to sourcing the bits even injectors, m30 afm, and chip to suit soon ends up costing a lot for the gains you get, esp as some say they get good gains, others say nothing really!

[87mtech27]

Pete has a 2.7 block

[steve_k]

If you're you are struggling to find an eta 2.7 crank you can use either a m50b25 nv crank or an m52b28 nv crank.

[ZoomeR]

NA tuning is crappy stuff. Unless you have some kind of limitations for the race groups or because of the country laws, go with 24v bigger displacement engine or turbo.
I've gone down this road with my daily driver e46 328i after installing intake manifold, s50 headers and s52 cams I got meager 20whp and 4Nm - totally not worth the money and time invested.
If you want to keep low budget, get a shorter diff (you can get up to 4.45 from e34) or a e36/46 tranny.