throttle body change

[Guest Andrew]

Yeah, i've got the 325i T/B aswell, the 320i rubber boot fitted onto the 325i T/B with a little work so no need to get a 325i one.

This is definately a must for 320i owners.

i'm fairly sure the dia. of the AFM is alot smaller also on 320s.

Nope, the AFM's have the same diameter, just the boot on the 320i tapers down to a smaller diameter at the TB whereas the 325i doesn't taper, besides, it's not the AFM that's the bottle neck

regardless if its the bottleneck - its still the most restrictive part of the whole system

[Coffee&Doughnut 0]

Well got the 325i TB fitted, ground away and polished the intake entry to create a good match for the TB, also attacked the manifold with a rotary wire brush and a steel scowrer, came up like new worked a treat.

So far cant tell if its faster, it revs quicker, feels smoother, not as congested when going at 40-60kmh, a little more responsive and its not running as rich.

It does seem that the AFM produces a bottle neck that and/or the entry to the airbox/filter.

[Carl 3]

Yip, it definately revs faster and feels smoother

[Coffee&Doughnut 0]

Yep I reckon it is faster too, took it out on a familiar stretch of road and topped the usual speed by about 10kmh on a relativly short run. Not a particularly accurate test but satisfying all the same. :bounce:

[Gus 5]

putting my bigger one in didnt make a big difference, maybe seemed a little more torque and smoother, but otherwise relatively the same

[Coffee&Doughnut 0]

Just a question regarding fuel economy, I have noticed my fuel consumption increase since changing the thottle body

I used to average about 10l/100km. I think now its more like 10l/ 75-80km same kind of driving .

What direction should I be looking in to fine tune the air fuel mixture and regain some economy? Custom chip/ ecu? Idle control valve?

[Gus 5]

more power = less economy, when you trying to fool the stock ecu, there not much it can do

[Carl 3]

more power = less economy, when you trying to fool the stock ecu, there not much it can do

Stop talking bullshit, more power does not always equal less economy

[Coffee&Doughnut 0]

Thats what I thought, maybe is it possible to reach a compromise. I thought of maybe

swapping the stock chip back in to see what happens.

But beyond that I dont have any idea what could be done if anything. I dont mind burning a little more fuel but maybe a little less than whats being burnt now.

But I reckon the manual conversion would balance things out only my diff is 4.27.

[Carl 3]

I find the stock chip in mine with the t/b changed is running alot better than before without, definately getting better milage out of the fuel swingometer, better all round

[Coffee&Doughnut 0]

That sounds interesting, I dont think the swingometer is as useless as people make it out to be. I will try out the stock chip in the next few days if i can find it. See how it goes.

[Carl 3]

That sounds interesting, I dont think the swingometer is as useless as people make it out to be. I will try out the stock chip in the next few days if i can find it. See how it goes.

I've found my swingometer to be quite accurate, or at the least, a damn good indication of what you're doing. You really need to ditch the auto box and stick in a low ratio diff if you're concerned about fuel economy. I had a 3.25 ratio diff a while back and that was getting me 44mpg, getting around 36 from the 3.64.

[ED1RTY 2]

keen as on this upgrade can i please have a list of bits needed and some basic instructions

[Carl 3]

keen as on this upgrade can i please have a list of bits needed and some basic instructions

Depends on your engine, with a motronic it's a straight swap (depending on whether you want to upgrade the rubber boot or just make it fit) but with L-Jet there's fiddling to do with the hoses. Just get the bigger t/b first then see if it's going to be a straight swap or if you need to do some fiddling.

[ED1RTY 2]

its an 87 320i m20 engine, do i need the afm aswell?

[Gus 5]

Stop talking bullshit, more power does not always equal less economy

no it doesnt

however doing it this way does

fool

[Coffee&Doughnut 0]

Finally swapped the stock chip back in the ecu, So far as I can tell fuel economy has returned to what it was roughly prior to changing the TB. It is pretty close. averaging 10km/1 L

Minus the after market chip the car runs much the same only difference I notice is lower idle speed, engine/ exhaust tone sounds deeper, I cant tell if it is any faster or slower, its smoooth.

But I think the TB mod is better than the chip alone in my case. not a bad compromise. If I am going to be burning a litre per 7km in a small car I wanna be doing 0-100 in 6.5 seconds or under.

[Guest Andrew]

smooth - m20?

[Coffee&Doughnut 0]

Smoother than before.

but its all pretty subjective I admit.

[Carl 3]

smooth - m20?

Yip, feels alot smoother, but i'm waiting for a dyno run to see what's really happened

[Coffee&Doughnut 0]

I would like to see dyno results too but I cant see myself doing one anytime soon.

I am at a bit of a loss with the M20 2l, I am still hesitant to cut the cat out in case

I lose any low end torque not that it really has any to beguin with.

[Carl 3]

I would like to see dyno results too but I cant see myself doing one anytime soon.

I am at a bit of a loss with the M20 2l, I am still hesitant to cut the cat out in case

I lose any low end torque not that it really has any to beguin with.

Woah, if you've got the stock twin pipe exhasut then cutting the cut out will increase your entire torque range, it made a massive improvement to my car.

[Coffee&Doughnut 0]

That sounds reassuring, Would twin 18inch hotdogs keep the noise/ sound within

similar range?

[Carl 3]

That's what i've done, I stuck a coby resonator on each pipe and the noise is still comfortable, but the car becomes much more rev happy and responsive.