2.5 throttle body on my 320

[potman]

i have read that i can increase power on my 320 by fitting a 2.5 throttle body and inlet manifold. has anyone ever done this?
dose the 325 setup have a larger internal diamiter?

thanks for any advice.

[Cloggy Saint]

You'd need to port the inlet side of the head to match the larger 2.5 manifold. It's supposed to give quite good gains to a 320.

[hongkongfuey]

i read in a bmw magazine, they did a project with a 320, they put on the 325 tb , they had to grind the opening so the throttle butterfly doesnt foul the manifold, then chipped it too, they reported it to drive like an average 325

you could put on the 325 manifold on as well , but some say you would loose some low down grunt???

[Brianmoooore]

The chip and 325 TB will make noticeable improvements to a 320, but it'll still be a long way from a 325.
These sorts of gains just aren't possible from engines by tinkering around the edges!
The best advice, is to enjoy a 320 as it is, change it for the complete 325 engine, or keep the head and stick a 525e 2.7 bottom end under it.

[potman]

you could put on the 325 manifold on as well , but some say you would loose some low down grunt???

the 320 has preicous little low down grunt as it is in my opinion. i have4 a 2.5 tb and manifold sittin about so i'll try that.
has anyone ever put a 325 fule pressure regulaitor on a 2.0? i heard that that would increase low power.

[AndyTouring]

the 320 has preicous little low down grunt as it is in my opinion. i have4 a 2.5 tb and manifold sittin about so i'll try that.
has anyone ever put a 325 fule pressure regulaitor on a 2.0? i heard that that would increase low power.

The 320 has either too many cylinders or too little capacity depending on how you want to look at it. More cylinders means more internal friction & drag so you need more capacity to counteract this.

The 320 was all about smoothness not performance. Yes it was somewhat strangled in standard form so as not to be too close to the 2.5 but don't forget, the 2.5 is quite peaky too.

Fuel pressure regulator giving more power? Why would it do that? Best you could hope for is just using more fuel.

Basically, if the 320 isn't fast enough for you then get a 325 instead. It will be far more effective & probably cheaper than messing around with bodges.

[hennabm]

I'm running a 320 manifold ground out to take a 325tb. If you look under the Article section at the top of the page and under technical (I think) it tells you how. The grinding - I used a normal B&D drill with the attachment. Took me about an hour before I was satisfied with the finish. A new 325 tb gasket from the dealer and job done. I did have the manifold off duing this opertaion and after washed it out with gunk and water then took it to a mate who used an airline to blow it out.

I'm going to chip it but at the moment the only difference I feel is pick up mid range where it is more responsive than before. It has also lost a big flat spot it had on accelerating from standing.

Certainly it will never be a 325 but it does me. What can you buy for £70 and I'm talking the whole car!

[Templ8e30]

Read this http://www.e30zone.net/modules.php?name ... tbconv.htm

Don't fit the 325i fpr or injectors, there's no gains to be had.

Cheers,

Iain T

[DavieP]

I'm going to chip it but at the moment the only difference I feel is pick up mid range where it is more responsive than before. It has also lost a big flat spot it had on accelerating from standing.

Out of interest, has this had any effect (good or bad) on your fuel consumption?

[jaistanley]

I sincerely doubt the 320 pulls enough air to choke it's throttle, and if it does it'll be high up in the RPM range. To me the gains people are reporting are due to a larger throttle area for the same pedal input, ie, the same as pressing the pedal in further. OK so there will be slightly less throttling losses but if you know what they are, you know it's not that.

Of course I could be wrong and the 320 does choke it's throttle, but the gains in that case will be as the engine approaches the oint where it's chuffing the most air around.

Changing to a complete 325i plenum aswell could well change the torque characteristics of the engine if the runners are of a different volume. I doubt it'll increase the power significantly, possibly the area under the graph will be slightly higher. If you're going to the effort of bolting in a new plenum and throttle, leave the big heavy bit at the bottom attached.

[StuBeeDoo]

the 320 has preicous little low down grunt as it is in my opinion.

Fitting a 325i TB won't change that. Trust me - I've done it. What the TB mod will do is make the car fly above 4k rpm.

Fuel economy is not much different unless you drive it like you stole it all the time - then it's worse.

[hennabm]

I'm going to chip it but at the moment the only difference I feel is pick up mid range where it is more responsive than before. It has also lost a big flat spot it had on accelerating from standing.

Out of interest, has this had any effect (good or bad) on your fuel consumption?

My fuel consupmtion has worsened. The OBC used to show around 12km/l around town. Now its about 15 km/l.
Still it's only a toy. I'm hoping that chipping it will help sort it consumption.

[StuBeeDoo]

My fuel consupmtion has worsened. The OBC used to show around 12km/l around town. Now its about 15 km/l.

Surely that's an improvement?? You're getting more km's per litre!

[Cloggy Saint]

It used to use 12 litres for every 100 km, now it uses 15

[hennabm]

It used to use 12 litres for every 100 km, now it uses 15

datourer got it - I just had the litres and Km the wrong way round.

[AndyTouring]

Well the advice is still the same. If you want more power, do what BMW did - fit a 2.5.

No matter what you do, that extra 1/2 litre is is going to count every time. Why do you think 2.7's are so popular? Tuning a 2.0 litre will only give power gains at the top end of the rev range - just where you don't want them.

Since a 2.5 engine is £150 - £250 (correct me if I'm wrong on prices) then that's the cheapest way to get a 40bhp power increase + the extra low end torque which is what you really want.

Fannying on with fuel pressure regulators, 2.5 throttle bodies, cone air filters sucking in warm air etc. is a complete waste of time, money & effort and will probably lose you more power than you gain. If you absolutely must have more power (other than to impress your mates at the bar) then make the effort worthwhile - just get a 2.5 as jaistanley advocates.

"It used to use 12 litres for every 100 km, now it uses 15"

In old money that's a drop from 23mpg to just under 19mpg (which is the same or worse than I get from my 635 auto). So do you think the improved performance from your 2.0 litre is worth the 21% drop in economy, especially since it's likely to be at the high end of the rev range (ie. the bit you spend the least amount of time in)?

Don't get me wrong, I'm all in favour of improving the product but these days (and that includes the late '80's) such increments are marginal - just ask Alpina & co how hard it is to make gains.

Unless you're changing the cam, valve sizes (& possibly inlet/exhaust to suit) you won't be gaining enough to make it worthwhile - trust me, BMW would have done it already. This still leaves the question of peaky power delivery which can only be answered by a capacity increase or forced induction.

[hennabm]

Well the advice is still the same. If you want more power, do what BMW did - fit a 2.5.

"It used to use 12 litres for every 100 km, now it uses 15"

In old money that's a drop from 23mpg to just under 19mpg (which is the same or worse than I get from my 635 auto). So do you think the improved performance from your 2.0 litre is worth the 21% drop in economy, especially since it's likely to be at the high end of the rev range (ie. the bit you spend the least amount of time in)?

.

As it's only a toy I'm quite happy with it. As the car came to me for only £70 I really didn't care if it was 2.0; 2.5 or even 2.7. It gives me a smile factor at a cheap cost.
Thing is my old 323i is standard and will only return 24mpg and has done all the time over the 21 years I've had it, so thye differenc eisn't that great when measured against that.

[AndyTouring]

The point I was making was that the 5% or 10% (at very most) power increase that you'll struggle to notice is out weighed by a 21% drop in economy. That's not improving efficiency, it's making a trade-off.

Cheap toy or not, I can't really see the point if you aren't going to gain something from your effort. Better to spend the money on refurbishing suspension, interior & bodywork. At least you'd see the difference.

21 years with the same car? That's more commitment that a lot of people give their marriage!

[hennabm]

The point I was making was that the 5% or 10% (at very most) power increase that you'll struggle to notice is out weighed by a 21% drop in economy. That's not improving efficiency, it's making a trade-off.

Cheap toy or not, I can't really see the point if you aren't going to gain something from your effort. Better to spend the money on refurbishing suspension, interior & bodywork. At least you'd see the difference.

21 years with the same car? That's more commitment that a lot of people give their marriage!

I would agree it's making a trade off. Quite often in the "good old days" a power increase meant worsened fuel consumption, so I'm OK with that. As for the interior - that came free from fleabay and as for the suspension - I'm waiting for an Eibach ARB kit. Just fitted a s/s sports exhaust. Sounds great!

The old 323i I bought when 4 years old and she is still with me. Like a good woman it doesn't argue or complain and does everything I tell her! All I have to do is feed her and keep her looking at her best which is the expensive bit!