E36 323i intake swap results

[Beaubot 4]

Ive got a e36 323i with the m52b25, which also has the restrictive obd2 intake. It had 315000kms on it when I picked it up several months ago, mustve been a reps car as itd clocked 250000km in just under 3 years and it still runs amazingly well.

The auto was starting to slip when I go the car, first modification was a manual conversion with a lightweight flywheel (from one of Bimmersports members) which made it so much more of a drivers car. Also the factory auto diff ratio coupled with the manual gearbox ratio is great for acceleration but theyre less than desirable for highway driving.

Ive just put the m50b25 intake manifold on last weekend and the breathing improvement at the top of the rev range is significant enough that its noticeable. With the old intake you could feel the engine choke around the 5500rpm mark, where as now it still spins freely to the rev limit.

I had a pre intake dyno run done and Im just waiting for a chance to do a follow up, will post results when I have but Id recommend it.

[Beaubot 4]

Well, had the follow up dyno run today, results weren't quite as good as Id hoped. While the car feels much freer at the top of the rev range, turns out power and torque have dropped over nearly the entire rev range...... I do however have another 600rpm to use which is kind of strange.

Please bare in mind I have done absolutely nothing else to support the manifold swap but I guess this dispels the rumours of "15 to 20hp" gains just by swapping the intake manifold.

Blue is m52 manifold, red is m50

[Michael. 2313]

That is pretty damn interesting.

Glad to finally see this on a dyno... ~7% peak torque loss!

[Beaubot 4]

Keyboard WARRIOR!!!!! calm the farm 3pedals, I hope you dont speak like that to peoples faces.

Ill admit I didnt do too much research specifically on bimmersport (so I didnt see your thread from 5 years ago) but as with the glory of the internet there were plenty of sites and forums internationally that supported the swap, the manifold cost $60 from pick a part and the dyno runs cost nothing. I am aware of the torque loss but Im, fairly happy gaining another 600rpm. I still have the m52 manifold but I think Ill keep the m50 manifold on the car.

If I were really wanting heaps of power Id simply drop in my L98 and be done with it.

Michael, cheers for the slightly more positive reply

Edited May 26, 2013 by Beaubot

[_ethrty-Andy_ 2136]

everywhere you look it says there is an increase in power and a decrease in torque, but the decrease not usually this much, i would say its because you have an M52B25 not a B28 which is what people that usually do the mod have.

[Beaubot 4]

everywhere you look it says there is an increase in power and a decrease in torque, but the decrease not usually this much, i would say its because you have an M52B25 not a B28 which is what people that usually do the mod have.

Yeah I had read that midrange torque would suffer, overall power would increase and that the engine would run freely up top. I can vouch for the extra revs and the fact the engine doesnt choke up top and I suppose there was a 1kw power increase (lol) Either way Im still happy with the result, I enjoy ringing the tits off the old girl and she seems to love it. Many of the US based sites still recommend the conversion for the b25 (I can only assume they were more common)

I just thought Id share, especially since Jonathon provided me with some dyno runs

[_ethrty-Andy_ 2136]

i wonder what would happen putting an M52 manifold on an M50

[Beaubot 4]

Well when the M50 was released I wouldve been 3, so I cant say it was too high on my list of concerns.

I understand what youre saying but in my eyes I have gained 600rpm, the engine will rev 600rpm higher before it limits, power delivery is more linear and up top she spins freely (where as it used to have a significant choke point) It would be interesting to see what sort of results tuning could yield.

For a cheap road car Im happy with how it drives and performs, all I need now is an LSD. Despite the torque loss I still feel the car drives better. Like I said if I wanted cheap power I wouldnt be pissing round with an old Bmw donk.

[Allanw 1072]

the engine will rev 600rpm higher before it limits

If you've only changed the manifold, the rev limit is still the same - it's ECU determined.

[Beaubot 4]

Agreed Allan hence why I said it was weird, the engine physically revs 600rpm higher now before the rev limiter is cutting in. I can only assume its due to the smaller manifolds choke higher in the rev range.

Lighten up Ron. I understand many people are so concerned with numbers, power figures and so on but in my opinion my car is now better to drive, how does that make me delusional?

Just because someone doesnt agree with you doesnt mean you need to be an ass about it

[Beaubot 4]

So why do you keep coming back to have a go? When I posted my dyno results and my initial posts did I ever ask for you to weigh in with your opinion? I was simply sharing some facts that I have encountered.

When I searched the forums for info on 323i intake swaps your "5 year old" thread didnt turn up so how was I to know that you had already done some research? For some reason you seem so offended that I shared my findings.

I know what my car was (and is) like to drive, the torque loss isnt noticeable but the extra revs are, hence why I prefer the car as it is, not to mention the power doesnt feel as if it drop off so significantly, power delivery feels more linear (which you can see in the graph)

What was my obviously stupid comment? That I FEEL my car drives better? or that I like having the engine spin an additional 600rpm?

Hop down off your superiority complex high horse and realise its just a BMW forum, theres no need to act like a hero

[jom 98]

Agreed Allan hence why I said it was weird, the engine physically revs 600rpm higher now before the rev limiter is cutting in. I can only assume its due to the smaller manifolds choke higher in the rev range.

Lighten up Ron. I understand many people are so concerned with numbers, power figures and so on but in my opinion my car is now better to drive, how does that make me delusional?

Just because someone doesnt agree with you doesnt mean you need to be an ass about it

M52 328 + M50 Manifold = 1.28.5 at Manfield. I put it in, won't take it out until (maybe) I go manual. As I've said before, it suits the auto box better. It is still noticably quicker than a manual 325. (or 328 on a good day...) Main problem with the auto is the short shift due to G loading exiting Higgins.

[Beaubot 4]

That Ron was a great reply, see we can all get along.

Youre right about the subjective opinion, its hard for me to explain but the lack of restriction at the top end is quite a significant change in the way the engine runs, I understand Ive lost power and torque but its just more enjoyable.

I guess if you factor in that this is just a cheap daily that I rev out repeatedly and not something Im trying to do time attack with it might make more sense. If not, no matter.

From what I could find the 323 has the same headers as the 328 but has restrictive single down pipe? It appears mine has had a bit of a replacement section at the y pipe but its still not all that large in diameter. Other than that Ive binned the cat, run a nearly dead straight 2.5 inch pipe to the rear and have a high flow muffler at the bumper.

Edited May 27, 2013 by Beaubot

[Ahmedsinc 414]

Here is the dyno graph , note engine also produces power further up the rev range max power up from 5,300RPM to about 5,700RPM. and the dip at 6,000 is almost gone, this engine easily hits the rev limiter in 3rd & 4th and hits the speed limiter (255)

Note this graph is with no other mods just the exhaust.

My calcs give about 145 kW with Schrick intake and a remap.

That's a nice gain on the torque curve!! Was this using the stock air intake?

And where exactly would one find S50 headers. WITHOUT taking a second mortgage to pay for them?

[Ahmedsinc 414]

The intake manifold is a stock M52 manifold, air Box is from an M3 and the snout is connected to the brake air duct and the section around the headlight is modified.

This gets more air into the MAF and throttle body and there fore into the manifold without loosing velocity through the manifold , which is the issue with using an M50 manifold.

With the M50 the restriction is ahead of the MAF so the air coming into the manifold slows down - this drop in velocity affects the torque delivery.

Headers were $600 second hand - homework and detective work pays off

Likey likey! Right, something worthwhile for the 325i - the hunt is on for either a genuine set or cad drawings to make 'em myself

[Allanw 1072]

isn't there a difference between the Jap exhaust, and the Euro ones on E36's? I thought the jap one were more restrictive too? Maybe related to the Jatco box?

[Ahmedsinc 414]

isn't there a difference between the Jap exhaust, and the Euro ones on E36's? I thought the jap one were more restrictive too? Maybe related to the Jatco box?

I know the M52 E36s run to a single pipe as opposed to the dual 2 and a bit inch stainless system on the M50s. From what I've seen the system on mine is identical to the NZ new and UK imports. Not fantastic, but certainly a less restrictive setup than the 323s. More so after I rip the clogged up old cats out and biff them in the skip!

Don't know , have avoided jap imports as they have been so unrewarding to test drive.

It would mean that the gain would be more noticeable but only because its based on a lower starting point.

M52 2.5 should easily crank 120kW at the rear wheels

Any gain for a reasonably small sum is a good one!

[gtstarped 73]

How about converting the 323i to a 325i? I have an auto loom/ DME/ injectors/ airflow meter from a vanos 325i which shoud increase your power to the stock 325i power? I'm sure I've read about this online somewhere, maybe worth searching.

Oh, I've done a M50 on a 328i too + 3inch exhaust, massive difference, revs harder and harder with more revs and with a ECU upgrade would rev to 7000rpm clean I reckon.

[BM WORLD 1286]

thats funny

here is my 328i coupe from a few years back

made 111.8 rwkw

3.15 diff , headers ,std exhaust with cats , 6.5kg flywheel 5pd manual .

100,000km on the clock

full power at 5200rpm 295Nm

my old 92 325i made the same power 111.9rwkw with same diff and flywheel , std cast manifold std centre exhaust ,after market rear muffler, chipped ecu ??

200,000km on the clock

full power at about 5800rpm 250Nm

my mates 328Ti we just made up has a m50 325i intake manifold and throttle body ,stock 328i ecu etc 7kg flywheel , 5spd manual , std headers , free flow centre pipes ,

stock 318ti rear muffler , 3.64diff 160,000km on engine

made 126rwkw and 295Nm

[Michael. 2313]

Loo at the torque cures, specifically the middle one from Brents' 325- the torque drops with an increase of Rpm right across the range.

Isn't that the A/F ratio graph line in the middle sheet for the 325i?

[BM WORLD 1286]

Isn't that the A/F ratio graph line in the middle sheet for the 325i?

correct , didn't get a torque curve on that dyno run.

[hybrid 1044]

pro tip.

Have a look at the green figures on your graphs .. if the intake temperature (IT) is out more than 5 degrees you will see power loss on the higher temp graph.

DMEs compensate quite a bit using an intake temp map.

[uniqueautobodies 0]

hi I have a 1999 e36 323i auto and have just swapped in an intake manifold and throttle body from a 325i

not only has my traction light come on but I have a significant loss in power???

feels sluggish and powerless

am I better with my original manifold?

[yng_750 247]

sounds more like you have put it into limp mode or similar.

[uniqueautobodies 0]

sounds more like you have put it into limp mode or similar.

not in limp mode no still drives fine no issues, just feels like ive lost 20bhp or something

could it be restricting it more than my standard 323i inlet?