60 BHP 2.7l? Why????

[327ire]

So the question,....

Iv rebuilt the stock eta 2.7 bottom end (new piston rings + small end bearings) and strapped on a 325i head, plumed in the turbo to the exhaust /oil but not the intake. Im running the engine stock everything (fuel / air) n/a while i break it in.

The car feels like its putting out around 60 bhp!!

I jacked up the back to see if it ran ok without drag. It ran fine in each gear and at any speed. On the road it runs fine but seems to have very poor power.

Any suggestions why this is happening?







And now to the project thread.....

Some of you may remember i started a rear mount turbo build aaaaages ago. I managed to destroy 2 old turbos due to problems with the oil feed (my ignorance really) and by that time a turbo manifold was down to 160€ so i decided to re-start.....




Donor...



Manifold from eeeeee bay....





Intercooler from a 3l TD transit





Rat look the sh$t out of me bonnet...



2.5 inch flexi exhaust



2.7 eta stock bottom end. New piston rings and rod bearings. 325i head. The pistons in this are concave, convex on the standard 325i. This means that the compression will be lower than the stock 325i, 8.8;1. This should give me something like 8.4.1 but i seem to find different results on every turbo thread! Should be OK off boost, and safe on boost. Pity the pistons are not in better condition.

[GeoffBob]

So the question,....

... plumed in the turbo to the exhaust /oil but not the intake. Im running the engine stock everything (fuel / air) n/a while i break it in.

The car feels like its putting out around 60 bhp!!

Not exactly stock! The flow of exhaust gasses from your engine is obstructed by your turbine. This will result in back pressure, which will reduce your engines "stock" performance noticably.

[327ire]

thanks geoff!

I cant imagine that the turbo would make the engine run 70% less efficient though? I know the lower compression + the exhaust restrictions would make some difference but 70%? The car is undriveable as it is. Im using 320i clocks so the rev counter is false but the turbo does not seem to boost until quite high rev's. It does spool and blow consistent air at idle and through the rev range.

thanks again for the input!! keep it comin lads!

[Gunni]

Are you actually running the compressor open?
This can kill it very fast.
It also leaves the wastegate closed at all times.

And why would 320i gauges show the rev counter wrong? They´re both 6cylenders.

How far have your driven it now?

[m_jermyn]

Ide take what Gunni says as gospel on this one.... He is the turbo king and im sure he will have you sorted out.

Good luck, looks impressive.

Mike

[327ire]

Thanks gunni. The clocks were always wrong when i got the car as a 2.7, reving out over 10,000 rpm so maybe they are 4 cly clocks?

And the compressor is running through the intercooler but is left open at a 2" pipe.

I would imagine that the wastegate will be closed at low rpm to encourage the turbine to spool and only open when its reading Xpsi?

[327ire]

Im not reving over 3- 4k. Do you mean that the turbo is getting killed on an open compressor or the power?

Its only done about 3 miles (1 hour insurance) and about 30 mins idling.

[GeoffBob]

I would imagine that the wastegate will be closed at low rpm to encourage the turbine to spool and only open when its reading Xpsi?

So long as your intercooler outlet remains disconneted from the engine inlet, your compressor cannot build any pressure (it is essentially open to atmospheric pressure). For the wastegate to open, the compressor must be able to build pressure.

FYI, a turbocharged engine is effective because the pressure across the turbine is more than compensated by the pressure at the inlet to the engine. Start blocking up your exhaust tract, even marginally, and (with no pressure at the inlet to compensate for this) you will see your engines performance rapidly decline.

[327ire]

Logical stuff there.

So the turbo will not spool up properly unless its actually piped into the inlet system. That might explain why even at 3500rpm there is little air coming out of the charge pipe.

So,.. ill pipe it all up and plum in the FMU just in case I do boost. Heavens forbid

[GeoffBob]

Im not reving over 3- 4k. Do you mean that the turbo is getting killed on an open compressor or the power?

You're running the risk of spinning your turbo too fast. With the compressor disconnected from the engine the turbo essentially runs without a load and the spins freely. Without feeling the "load" on the compressor (due to the work that the compressor does in flowing air into the engine under pressure) the turbine will over-speed if you are not careful, with potentially catastrophic consequences.

The correct way to run in a turbocharged engine is with the inlet tract pressurised (that is to say, with the turbo under load).

[m_jermyn]

It will spool up but its not putting the compressed air back into the engine.. Its just blowing it through the cooler and out the other end... Connect the outlet of the cooler to the inlet of the motor and it will work..

What you have done by connecting the turbo up is basically block off the exhaust which restricts the engine... Take the turbo off or connect up the cooler then run it in...

Mike

[GeoffBob]

Logical stuff there.

So the turbo will not spool up properly unless its actually piped into the inlet system. That might explain why even at 3500rpm there is little air coming out of the charge pipe.

So,.. ill pipe it all up and plum in the FMU just in case I do boost. Heavens forbid

Sorry, my last post fell out of sequence. I think you posted just before I did, so I hadn't seen your last post when I posted mine.

The most likely reason you're not feeling much air flow out of your turbo at 3500rpm is because you're doing this test (I suspect) out of gear on the garage floor? IE, you're revving the engine to 3500rpm at only part throttle. Barely cracking the throttle on the shop floor (which is all it takes to get your engine to 3500rpm) won't flow enough air through the engine to spin the tubine hard enough for the compressor to put out very much air at all! Remember, the speed at which your turbo spins is dependant upon how much air you induct through your engine, not how high you rev your engine (although the two are generally related).

If, however, you were to try this same test out on the road (how dangerous would that be?) with the engine under load at wide open throttle, you'd experience a wholly different result! You'd be foolish to try this test though (even on a dyno) as you run the risk of over-speeding the turbo. Turbochargers have rev limits just like engines do.

[327ire]

Great stuff there boys. I was worried that my turbo choose was too big .63 cold .63 hot.

I suppose the only thing to do is pipe it up n try it again. I am still worried that the engine is crap off boost though. I'll let u know later....thanks again lads

[Gunni]

Your engine is run in now.

all the exhaust energy is going through the turbine, as the wastegate can´t be reading much boost for it to open. So your compressor speeds are way way to high and could lead to failure.

You should never leave a compressor like that unloaded, you could have run it in with everything plumbed up as it should be, just not boost and you´d be good.

But since your engine is run in now it´s time to fit some management and get it tuned.

[eta]

Also an stock eta bottom end with an 885 head gives you 9.35:1 CR. What boost you can run safely from what I understand depends on the grade of fuel you use and the temperature of the intake charge (intercooler efficency) amongst other things.

[327ire]

So the update....

It turns out the NEW walbro pump is scrap! It was putting out about 3-4 bar unsteady. So the OEM went back in and its much much better. My mate had the same problem with that pump. Bastar@s!

So now its driving better, more power. Im not sure if its 2.7 standards though. Iv 200 miles on the break-in so I took her out with the turbo piped + blow off valve + FMU. JEAAAASUS! What a noise! But no boost on the gauge even though the turbo sounded very active. Maybe the wastegate needs attention, maybe boost leak.

"eta"
Forgive my ignorance but does my setup now give me higher compression than a stock 325i? If so, woops! It is a 885 head on stock late eta.

[eta]

It depends on what year your 325i came from. Early ones had a diferent compression ratio to later ones. Early (pre sept 1987) pistons gave the M20B25 a 9.75:1 CR later ones gave the M20B25 a 8.8:1 CR.

[appletree]

Was wondering what happened to this car, was realy hoping you would get some good results with the rear turbo

[327ire]

Yeah pity alright. I just got completely pi$%ed of when i ruined the first turbo with a lack of oil, the second too much, and then after the re-build I rang the shaft nut! So I lost interest and the turbo manifold became a cheap buy.

So.......

Lots of stuff to report. One of the charge pipes came loose so i connected it and had some fun. Boost gauge shows 8psi and the air/fuel shows optimal- rich mixture. It feels fairly fast.

BUT.....
Shes burning oil bigtime. So much so that cylinder 4 + 6 have stopped sparking due to clogged plugs. AND the sump gasket has pushed out and is leaking oil. There is oil coming from higher on the engine to, not sure where. Not huge amounts. I think the head gasket is OK.

So Ill get a compression check done this week but it looks like im getting boosted air through 2 cylinders and is pushing the sump gasket out. Not good.

Or could it be an emissions control problem? As in, the rocker cover breather or crankcase to inlet pipe?

Cylinder 6 (4 looks the same)



Cylinder 1,2,3 (5 looks the same)