Rolling road result - Down on power, and ideas?!?

[Incitatus]

Took my '89 325se to a local rolling road here in shrewsbury (Hoshy's dad) to see how it was running. Result was not good! 161BHP

It's got the Zone chip, ITG kit and BBTB fitted. Here's the printout

Strange thing is as you can see that the initial pickup is quite steep, it just flattens off when the revs get high. The emission results shows that the fuelling's ok.

My friend also took his car (known as the saint on here) and his was bang on at 171, and his engine is unmodified. Out on the road though neither of us can pull away from the other, they seem dead even. Also out on the road it seems to run well enough, you can feel the initial pickup as it shows on the rolling road, but it does not feel to backof at high revs.

Any ideas what might be going on with it. The one suggestion was that whilst the fuelling may be ok, but it might not be getting atomised properly at the higher revs.

Hopefully one of you guys will have an idea what it might be. Driving it out on the road it feels good though.

Any ideas??

[kam-325i]

Where in Shrews is that place ?

If it is a standard SE, then all the power is low down, as the SE is designed to be an "Ecomony" motor....

More info needed on engine

That dyno read out look a bit wierd, they normaly have engine RPM @ the bottom and the BHP & Toruqe readings up the side.

[Incitatus]

It's in Oxon business park, out by Shelton, Shropshire Automotive Services, it's Hoshy's dad.

I thought the SE was just a trim spec, the engine output is the same as any other 325i? It's not and 'eta' anyway.

Yeah the readout's a bit odd, not helped by being in KW anyway! He said he'll be getting some more kit soon that shows torque/rpm ect on the readout. I've been going to him pretty much since I've had cars (15ish years), good bloke.

Buy now I'm just really curious whats causing that to flatten out like it does..

[kam-325i]

Its a bit hard looking at that readout, as you really want one based on RPM and not Speed.

It might beaused by a worn cam not allowing the engine to breath properly at high revs.....

[Jon_Bmw]

I wouldn't be too disheartened by 161bhp, but i suppose you have done some mods. Does beg the question whether they are ever worth it. Bear in mind you car is 17 years old, 17 years of sludge build up doesn't help performance.

As for suggestions as to why, has it had a full service recently, if not do it with gen BMW parts. Decent oil(speak to oilman), check all the electrical components(AFM, blue and brown sensors etc etc).

How old is your exhaust, perhaps your baffles are breaking apart and semi blocking the exhaust.

Check compression, also is your mates that made 171bhp a pre facelift as these tend to make more on rollars.

You will not feel or really notice that 10bhp on the road really, it comes down to the driver somewhat. That must mean you are a better driver if you can keep up.lol.

[Bob_S]

I was going to say that the cam may be worn or the followers which would mean it drops off towards the top end

[Incitatus]

It had an inspection 2 service and cambelt change last April, and it's just have a oil service with decent oil (I checked oilman's thread)and a BMW filter.

The mods certainly made a difference. They were fitted incrimentally and I felt the change on each that was fitted. Out on the road it feels a lot quicker than the rolling road result would suggest. I think my biggest concern is that the curve was initially a lot steeper than my mate's car until it suddenly levels off. It tends to make me suspicious that something's amiss somewhere, and if that could be identified then it would make the difference.

The downpipe and back box are new, but the centre section does have a reasonable dent in it, and it seems a bit echoey. It doesn't sound restricted though.

Yes, my mate's was a pre facelift.

[Jon_Bmw]

I was going to say that the cam may be worn or the followers which would mean it drops off towards the top end

Yep this is definatly possible, but harder to check to see if it is worn.

[Jon_Bmw]

I thought your mates might be pre facelift, they always seem to make more power. They are slightly higher compression anyway so they have an advantage to start with. Kinda sucks for us facelift boys...until you want to boost it

[M5pilot]

There could be lots of reasons for the lack of power.

You could have a
worn cam,
injector problem,
fuel pressure problem,
AFM worn out so its running very rich.
You could have an airleak somewhere.
Valve clearances out.
Worn out dist cap and rotor arm
incorrect plugs
valves not seating properly
bottom end worn out a little and lost some compression

These are just some posibilities.

The first 325i I modded made 154 bhp with 6 branch, chip and intake mods. The next owner found problems in the head which had caused the low power output.

Everyone is always recommended to make sure the car is running well before adding mods. Adding performance parts to a sick car doesnt do anything and in some cases can make it even worse.

[Incitatus]

The emissions were checked when it was run up, and the mixture was fine at the higher rpm, so I guess that means we ca rule out anything relating to fueling issues or air leaks?

He did have the theory that the injectors weren't atomising the fuel properly so the fuel was there but not being burnt as quickly as it should.

It's always given the impression of running pretty well, that's why I was reasonably happy to get the mods. However, regardless of the bhp figure, the mods have made a difference to the drivability on the road without a doubt, so I'm happy enough with them.

Just being bothered by the thought it may be something simple...

[Ant]

what spark plugs fella ?

[kam-325i]

With the Air filter and BBTB, maybe you need a slighty wilder cam to take advantage of them and to balance out the curve a bit...

[M5pilot]

I fitted an Alpina Cam to my touring and its made a big big difference throughout the rev range. Really full torque curve now and it revs very hard.

[Templ8e30]

I thought the SE was just a trim spec, the engine output is the same as any other 325i? It's not and 'eta' anyway...

Correct, the SE is a trim spec. All late 325i engines are the same whether they are bum basic 325i's or 325i sports or even Motrosport cabs.

Cheers,

Iain T

[Simon13]

my sport made 163 on the rollers in the summer but 175lbs of torque

As the cars fuelling is ok, my guess would be on dizzy and rotor and plugs as a first port of call. not expensive to do and will give then engine a new lease of life if it's not been done

I'm planning on doing this to my old sport as i have never done anything like it on the engine since i owned it, but it runs really well. But who know when these things were done last? I've done it on my auto 325i and it made a huge difference to how the car drives, economy and made it alot faster!

[thesaint]

You will not feel or really notice that 10bhp on the road really, it comes down to the driver somewhat. That must mean you are a better driver if you can keep up.lol.

no, ijust dont like to thrash mine for no reason, i keep up...

[Incitatus]

I'll check out the plugs and distibutor, see what's the situation with them and report. I certainly agree that the torque figure is making up for what the bhp may lack.

I do really appreciate your opinions on this, thanks for your help!

[Ant]

make sure and fit some NGK plugs for a chrome bumper model, they are simply better and you'll gain a couple of bhp

^ proven on the dyno @ AMD a few years back BTW

[Incitatus]

The plugs are marked: Bosch Super R1 388 W8LCR. It's a post facelift '89 car. Are these correct?

Actually I've remembered that over a few mornings recently there's been a bit of a misfire on startup, but a quick prod of the accelerator sorts it.