Laurens

I still would presume that when not enough air can enter the turbo (too small inlet), there is to little air to be pressurised.

in other words, not enough air can enter turbo or even more importantly the engine, therefore not enough load can be put onto the engine (lack of power), creating enough pressure in the exhaust system to spoolup the turbo

remember that at WOT I still read a 5 hg vacuum on the gauge, while normally it would / should be close to 0 (off boost)...

About the crossover pipe system (I pressume my exhaust manifold) do you think that the end pipe (just before the turbo is to big?

MrGiggles

For some reason it completely slipped my mind that you are running a draw through setup. In that case you are right. If a turbo isn't supplied enough air, it can't pressurize it. But I think it would take a pretty strong restriction to make that happen.

I really should have taken another look at your build before posting. Is the turbo plumbed to both cylinder banks? I assumed you were running a typical crossover pipe system that V style engine usually uses. Where you have a conventional manifold on one side, and the other has the turbo mounted on it and a typical outlet on the bottom. Then you have a crossover pipe that attaches the two. Because of all the connections they're prone to leak.

I don't think the pipe size would have much affect on boost. Might introduce a bit of lag if anything.

Laurens

In fact, I'm running the turbo of a single bank. That might seem odd, but Saab cars used this in the past with good results.

I figured that the TD04H-13C which was used on a 2,3 volvo engine is sized correctly for one bank. Because my engine is a 5.2 L / 2 (only exhaust gases from one bank) = 2.6 (spoolup will be even quicker than on the volvo's)

This would mean enough exhaust gas to run the turbo. (Why not use both banks, I hear you think. That's simple, in that case the turbine spool up is way too fast, causing it to boost almost all the time, and therefore killing economy and driveability).

For balance,
My better flowing homemade exhaust manifold + turbo (creating a exhaust restriction) on one side, and the already bad flowing stock manifold on the other side, should balance things out a bit...


Also I had a look at the compressor map before. and at 4500 RPM it should be able to flow approx 360 cfm (max of turbo), therefore giving me 210 HP (now it is only 150 max).

So keeping that in mind, If I obstructed the intake to much, lets assume at least the half, It could only flow 360 / 2 = 180 cfm

180 cfm with my engine would give me approx 70 hp, which causes my car to feel and drive like ****.

My guess therefore the problem is on the intake side! Which also explains the high (5 hg) vacuum at WOT.

Does any one agree with this reasoning, let me know!

busa4

i didnt see anything posted about fueling. did you add a fuel pump and a boost reference rising rate fuel pressure regulator? do u have an wideband afr gauge installed? whats the cfm rating on your turbo? if your turbo is too small your engine maybe breathing more air than the turbo can produce. on a large engine like that two t3 turbo or one t4 turbo would work great. the volvo turbo maybe too small........

busa4

i went on squirrel performance. they have a turbo calculator. i punched in some numbers with your engine and your turbo and it doesnt look good.

Laurens

I did the same, I've checked things beforehand,

My car has an army specific cam, which generates a lot of torque, with not a lot of HP
Redline = 4000 rpm
max power already at 2500 rpm

Checked the carb again, that's a 285 CFM 2bbl Carter carb.
The turbo can breath 360 CFM, so therefore should be big enough

No additional fueling system needed, due to the drawtrhough setup, carb will adjust accordingly, and above all I'm running an Impco Mixer (originally designed for FI) capable of feeding 7L + engine's (just turn the power knop to fine tune

Again, I'm not looking for huge power, only good economy and additional torque for towing and offroad use

busa4

your turbo map maybe affected by the turbo only being run by one bank instead of two so less rpm in the turbo will be created causing less cfm produced by the turbo compresser. since that turbo is small for the engine it will need high turbo shaft rpm to create boost. 285 cfm carb seems a bit small for a 318 v8 engine.

busa4

sorry thought i read blow through instead of draw through. try running the turbo through both banks. if that doesnt fix it then i think a larger turbo and running it through both banks would solve your problem.

Laurens

Busa, You might be right, however I was already working on a different intake, so that I will finish first. Having High Vaccuum at WOT means a restriction afterall. So offboost it would be nice to have close to 0 vacuum when needed...

The 285 CFM carb is indeed SUPER small, yet this is an old army trick. Fit large engine's with small carbs, and therefore limit the power the trucks can make. This way, it would be very hard to kill an engine due to abuse.

If the modified intake doesn't work, I'll try a crossover pipe (at this moment the goal is to create a bolt on package, without the need of modifying the original exhaust system!)

Yet looking at the whole setup it should work (if not to much restricted), The Turbo is measured at 360 CFM with the volvo motor (2.0 - 2.5), so the exhaust flow of such a motor should be equal to half of a V8 (5.2 L/2 = 2.6).

It possible has a higher turbo lag, due to the larger manifold it has to fill, yet I'll be running only 7 PSI, so that shouldn't be a problem I imagine...

I'll let you know how things worked out! Hopefully this weekend I'll be able to test my new dropdown tupe style inlet with 60 mm inlet size (matched to turbo).

Otay1000

hi Laurens, I think what you need to look at is the different size of the turbo sides you are using. The turbine does indeed have to be sized for the 2.6 litres of your trucks single bank of cylinders. However your compressor is having to flow and compress enough air for the entire 5.2 litres of the whole engine. This is how Saab did it- their compressor was gigantic compared to the turbine side. The reason you are getting oil in your pipework is the Volvo turbo doesn't have oil seals on the compressor- it was fuel injected so therefore blow thru- no vacuum was applied to the compressor seals. the carb is applying huge vacuum and sucking the oil out past the oil deflector. Hope this helps you out! love to see the beast going right.