R19KET

Steve,

Weird, the shape of you dyno graph would indicate much more. Your figures are very immpressive, especially the torque.

Mark.

john banks

Why don't you run a bit more boost Stephen? Say just 1 PSI held to 17.5 in the midrange? The intake temperatures seem to stay less than 25 above ambient at 2.5 PSI more than what you are running in road use - but then my breathing is more restrictive than yours and you do live in a hotter part of the world! Did you find the higher back pressure led to you losing a lot of advance or have you not gone higher? Would be interesting to compare your airflow at 4000 RPM with mine at higher boost. But then your MAF might underread with the more laminar flow...

Cosie Convert

Big turbo Vs Wee turbo..........

Unless you are thrashing the small turbo way outside it's maximum efficiency area then the discharge temps will be the same on a big or small turbo (assuming both running at say 70% on compressor map) If you only drop a few % efficiency by operating out of range then this is proportional to the extra heat you add.
The charge pressure is by far the major element dictating compressor discharge temperature.

We tend to get hung up on pressure, Stephen quite rightly works on flow

To achieve flow you need a differential pressure, so if you can reduce your exhaust backpressure by say 5 psi it is the same as raising the boost - it will increase differential pressure and hence increase the air flow through the engine.

The large turbo scores by running with a low exhaust backpressure, the bigger turbine requires less pressure (but more flow) to achieve the same torque transfer to the compressor. Therefore 1.1 bar on a big turbo = much more air flow and power than 1.1 bar on a small turbo.

An aftermarket exhaust manifold has a similar effect by reducing the pressure drop from exhaust valve to turbine. The equal (long) primary pipes may also assist in cylinder scavenging at the end of the exhaust stroke, further increasing the differential pressure (flow) from the charge air into to the cylinder.

StephenDone

Hi Mark,

Thanks. btw, what appears wierd about my graph ? Maybe it's the different left and right scales making things a bit confusing. Depending on what graph you are looking at, there is one scale for torque, and one for power. Is that what it is ?

Hi John,

I might run a little more boost. Well, there is a dyno day on Saturday after all ;-) Trouble is, I'm running out of blow - my point about flow verses boost pressure. I may have low pressure in my manifold, but that's because it's fair belting out of my exhaust. I could produce higher peak torque, but cannot produce any more peak power unless I run more advance or less fuel, and that's getting too risky (for me) at these powers.

(I'm on the lookout for a VF28 by the way)

Cosie, you know where I'm coming from !

Steve

R19KET

Steve,

I was looking at the graphs on your site, although they don't show your latest run. I was refering to your torque graph, you know, the one that looks like a helter skelter

The way I read it, is the turbo spooled up, overboosted, peaking on the first hump. Then, either the wastegate was blown open, or the ecu sensed overboost, and opened the WG to lower the boost, over compensating, seen by the big dip.

Now the boost is below the target levels, the ecu (boost controller ?) allows the pressure to build again, which is why your "peak" torque is relatively very high for a TD04.

Personally, I would drop the boost a little at the lower rpm, to just below where the ecu cuts in. Then whilst it will reduce the first peak a little, it should fill in the dip, and smooth out the curve.

If I'm wrong, blame Mervyn, because he taught me everything I know Well, about helter skelter graphs, anyway

Mark.

David_Wallis

Sorry to part hijack your thread....

Andy..

I seem to remember reading that you wish you had bought a different fuel pump / pressure regulator... could you recommend any?? I am only going to use the car on a track at the moment.. Did you replace all fuel lines to up to the filter...(ie from rail to filter) I like the idea of the inlet on the turbo.. may have to copy you on that one! Do you think it would make a big differnce... How / where would you mount the maf??

Mail me if you prefer..

Mark... cheers for recommending that cutter... I tried it and neally had to weld a hole back up John, I recommend you get one of these and stick it in your drill and 'jiggle' it around as you like doing so much ... Your also scaring me with those formula's.... I might have to go do some work for a break now!

David

[Edited by David_Wallis - 4/23/2002 9:53:05 AM]

[Edited by David_Wallis - 4/23/2002 9:53:26 AM]

StephenDone

Hi Mark,

Yes, the first peak is a spot of overshoot. Dyno run was done in rather colder weather. Spike is no longer present in the summer. The second wider hump is not boost, but the manifold doing its thing. I overboosted to 17.4 PSI coming on boost and then settled on about 16.4/16.5 PSI.

Cheers

Steve

john banks

Oh, I suppose I'll have to look at the group buy on headers to keep up with all you guys