Well I’ve bitten the bullet and had the 328i “fettled” and had the infamous big bore throttle body and intake manifolds fitted.

A bit of history if you like to how the mods came around. The 323i and the 325i are both 2.5l M50 units, and the 325i kicks out 193bhp. Then along came the 328i, with a 2.8l M52 engine, and despite the capacity increase, still 193bhp. The 328i was marketed as a high-torque alternative to the 325i as engines were restricted to 193bhp due to German insurance reasons.

This aroused some suspicion in terms of the actual tuning potential of the 2.8l engine, and some investigation discovered that the intake manifold on the M52 had tiny internal bores in comparison to the M50. I’d estimate the M52 to flow maybe 30% less air than the M50 unit. However, the M50 manifold isn’t a straight swap, but can be made to fit with some clever bracketry and gaskets.

Also, there are clear improvements that can be made to the original throttle body. The original is on a bend and is made up internally of 3 separate radiuses. By machining these into one nice smooth radius, and enlarging the bore (and butterfly) at the same time, clear gains can be made.

In addition to the above, there is a restrictor inside the air intake hose (there for noise reduction it seems) which is easily removed, as can the snow guaze from the MAF.

Its acknowledged that these mods will see gains of up to 25bhp and 20lbft on an otherwise healthy engine, and as standard the engines seem to dyno at the manufacturers stated 193bhp. So I’m looking forward to an RR day to see just how the car is running.

But figures are almost irrelevant. The way the car drives is transformed.

The standard engine is nice and torquey, but is quite lazy, getting a bit breathless beyond 5000rpm. With the new bits the car comes on a song at around 4000rpm, pulling harder and harder all the way to 6300rpm. There is a louder induction noise, and the car really has a nice raspy note that begs you to hold the gear as long as you can. I’m yet to do any official timed runs, but 0 – 60 is despatched in around 6 seconds, and top speed now well over 150mph. But as I say, it’s the feel of the thing that impresses, really livening up the top end of the rev range and improving throttle response too.

So there you go, healthy gains for remap money, with the advantage of the bbtb and manifold being completely resaleable should you get bored, making the mods very cost effective. It also keeps the car a lovely, quiet, refined, torquey crusier when you want it to be, but a real hooligan when you don’t.

any pics??

A friend had this done to his 328 and was concerned about emmisions at MOT time, he needent have been, when his MOT test happened the chap at the garage told him that the BMW had "Melted his probe".

Not sure exactly what happened but the EGT's were silly high, did make the car better though.

Thought it wouldn't take long tom. - Got any pictures?

To look under the bonnet you wouldn't notice anything wasn't standard, so no pictures really.

Will find some of the bits side by side etc though

And melted the probe??? Dear god!!

Hmm time for water injection or a big intercooler to bring down the intake temps.

Of course if you're adding an I/C you might as well get a big FMIC and then slap the supercharger on it and get going

Sounds good mate

So how long before the new bits are off and put on eBay cause you're selling the car?

Lol, no I'm not 'charging it! :P

Have you done that !*&^ lock yet? :irked:

Have you done that !*&^ lock yet? :irked:

Errr, whats funny about my lock?? :confused:

Yes Nick, was a doddle when I stripped the old one down, just copied the numbers. It was 11 different tumblers after all!!

You can clearly see the difference in manifolds here.

Actually I've seen figures of 60% better flow quoted! :eek:

And one of the throttle body...

A friend of mine has these manifolds on his 328i

Along with further Induction/Exhaust Mods and a Remap he recorded 206bhp/207lbft on RR

Some sort of ball-park for you maybe...

If thats the case I think the exhaust/induction may be LOSING him power. I'd be gutted with just 206bhp tbh, hoping for 220bhp+.

omg Tom the claimed figures on internet forums might be wrong!!! don't tell these 180bhp+ remapped fabia drivers this

tbh Tom then getting it to 200bhp from 193 with nothing more than changing the inlet manifold is a decent gain of 3.5%

expecting 220bhp would be an impossible 14% in my own opinion obviously i would maybe expect a 300bhp+ car to gain upto 20bhp from an inlet manifold but it'd have to be a good one!

Ah, but as per the first post, the key to the gains is that the OEM one is deliberately very restrictive.

People seem to be quoting up to 240bhp

I'll be happy with 220bhp Certainly drives bloody brilliantly!

Will be interesting to see how removing the snow gauze has affected the AFRs on the rolling road day. With some MAFs the gauze or vanes are there to condition the airflow. The MAF is calibrated for this. Changing the feed conditions can alter the MAF output and thus the AFR.

Chris

Interesting Chris, not something I'd considered. Doddle to put back on though

Ah, but as per the first post, the key to the gains is that the OEM one is deliberately very restrictive.

People seem to be quoting up to 240bhp

I'll be happy with 220bhp Certainly drives bloody brilliantly!

exactly, it's just like some people seeing gains of upto 15bhp (10%) from swapping the standard (artificially restricted) intake for something like a GGR CAIS on the Fiesta ST

Lol, no I'm not 'charging it! :P

Go on you know you want to .....

Well the latest RR run gave me 215bhp, so very pleased with that. 22bhp increase for £400 on an n/a engine is pretty impressive by my standards!

Well the latest RR run gave me 215bhp, so very pleased with that. 22bhp increase for £400 on an n/a engine is pretty impressive by my standards!

That is a really nice result from the intake manifold. Hows the torque curve? Are there plans to do an exhaust or is it already done?

Chris

Exhaust is pretty good as stock, twin pipes all the way back. Lots of the 323/325 guys upgrade to 328 systems

Quite pleased with the curves!! :P

Exhaust is pretty good as stock, twin pipes all the way back. Lots of the 323/325 guys upgrade to 328 systems

Quite pleased with the curves!! :P

That is a very nice tune you have there!

Chris