If you can't beat em, at least get a tow

 

the doc's 450/400 daily driver is back on the road. went to the garage and the doc just about had the box in himself , saved my back a bit of grief anyways.

my own car is back and still has a full working gear box

 

So when's it going to Dastek?!

I'll be heading up again soon, when the gearbox(funny that innit, alway's gearboxes), get's sorted.

 

starting to have a rethink on jb's gt30r turbo choice.

I have always liked it over 5000rpm , especially when it's kept on the boil. the mid-range though has always been flat imo, for the first stab of WOT , with john limiting the boost. (forget all this bar of boost at xxxxrpm , it's where she really pulls from that interests me). today the car had a real nice kick from under 3800rpm , much nicer!!!

 

As I've discussed with T-uk I was trying to limit the AVC's peaks to 1.50 with 1.40 kg/cm^2 held in sympathy to the standard pistons and gaskets, and also because it had a nasty habit of just randomly detonating*. This did result in a slightly sluggish rise in the midrange with the following duty profile:

2500 90%
3000 55%
3500 49%
4000 47%
4500 47%
5000 47%
6000 47%
7000 47%

...and gear judge with +3, +2, +1, 0, 0.

Always seems to be a compromise depending on EGT, IAT etc.

Sometimes after a gearchange at 5000-5500 RPM it would come up to only 1.25 or 1.3 before rising up to 1.4, other times it would come around quickly.

*since the cooling (radiator thicker twin core, 71C stat, only 20% coolant mixture) has been improved it is far less likely to det, over more than one tank of fuel. It now seems happy to peak at 1.8 bar whereas it would only get to 1.6 bar before, quite a difference. As a result, I am a lot happier allowing it to overboost over my previous limit of 1.5. At least without det we will really be testing the pistons & gaskets rather more safely

New setup is:

2500 90%
3000 65%
3500 53%
4000 52%
4500 52%
5000 51%
6000 50%
7000 50%

...with a target of 1.60 to 5000, 1.5 at 6000 & 7000.

Maximum overshoot is 1.73 in 3rd gear as it happens

Poor pistons, but at least it feels responsive

 

Almost there

 

I will post some shots of the PowerFC maps below. Note the VE compensation in the airflow calibration, the unorthodox MAF calibration 5, the unique accel vs TPS table. Typically hits the 10000 load row at 1.40 kg/cm^2, but the timing runs a few more than is shown on the ignition plot for some reason, no compensations active, think a few others have noticed this on PowerFC.

 

LOL at Andy

 

As I suggested when you bought it, 1.8 mid, 1.6 at the top

In my opinion, if you're not maxing out a turbo then basically you are using one that's too big !

Andy

 

I'd agree, but somewhere in this topic is the word "reliable"

Think this engine is on about 13000 miles now.

Since the 2.5 and six speed, the gearbox has broken once and the engine twice. Not sure how I feel about that but I'm still learning

 

John,

Noticed your IGN vs AirT is set to zero... do you not have an air temp sensor connected? If not do you feel that for you it's not really needed?

Tony.

 

Not connected. In a variety of temperatures it runs nicely with sensible AFRs. I don't mind it being a bit richer when hotter.

 

OK cheers

Tony.

 

You've got waaaaay too much money, John.

 

Is that due to the efficiency of the compressor on the compressor map? (i haven't seen one. well don't think i have! lol)

Do you find you don't gain much if anything trying to keep 1.8 to the top?

 

I think you have a different compressor wheel Alan. Yours should be good for 1.8 to the top.

Andy

 

I'll have a look and measure what mine is.

Can you remember what size the compressor wheel was on your old turbo Andy?

 

-12 compressor which is 57/76mm
I think yours will be a -13 or -14 which would be either 59/76 or 61/82mm

Andy

 

A question then.... Can you run antilag off the Apexi Power FC according to that screen up there?

 

I think it's the same Andy.
Part Number on unit is "700382-5012"

 

Maybe your engine will be better able to make use of higher boost pressures even if the turbos are the same Alan - better cams, pistons, better engine balancing, use of octane booster. Maybe you'll get some of the "2.33 benefits" I see - it is simply a nicer engine than the stock EJ257 the way it breathes, resists detonation, revs, takes timing etc even with the same cams and turbo.

 

Possible John.

At this kind of power level it was always my intention to run OB to have a more controlled burn.
At the moment i use 2ml NF per litre. Don't know what benefit in terms of increased power this will give over pump fuel, i don't think it's much, but maybe you can advise?

What benefits are you seeing John? I'm impressed that you've pushed your boundary again on the 2.5. I thought you would have stopped at 1.4bar, ran it for a while and ordered a different capacity block.

 

Maybe another 25 BHP and lbft from that NF mix? The 2.33 seems to run cooler, rev better and spool up virtually as well as the EJ257 I think.

I am often running 1.4 bar, but I am happy to use and thrash it running 1.6 bar through the midrange, still dropping to 1.4 at the top.

I am presently researching whether it is possible to use a pair of TD04s in a sequential setup, looking at flange compatability with VF32 and VF33. The Legacy twin turbo plumbing is a bit of a dog's dinner, valley of death can be Ecutek'd out. I think a 2.5 would be quite well matched to one TD04 low down, with full boost at about 2000 RPM, and smoothly bringing in the second one. If I had a pair of non-boost creeping turbos and the right valves in there I think I could implement a nice control strategy with the electronics, I have all the code to read load, RPM, power solenoids/relays etc.

http://www.johnbanks.dsl.pipex.com/twin%20turbo.jpg

BMW have a few interesting tricks on the 535d, and the Supra is worth getting ideas from.

http://www.johnbanks.dsl.pipex.com/BMW1.jpg

http://www.johnbanks.dsl.pipex.com/BMW2.jpg

 

It's unclear on the BMW drawing what happens to the primary turbo exhaust post turbine, I suspect it goes to exit but I would be inclined to run it through the secondary turbo at low rpm just to ensure minimum temperature/rpm gradients.

The need for an exhaust cross pipe on the flat4 is an inconvenience and source of inefficiency regards pulse strength, much better to mount both turbos at the front

You will recall what my 2.33 was like during 'run-in' on the TD04 John Just like a 5 lrt n/a engine

Andy

 

You got any RR figures for the car as it stands now John? Or what you think it might have?
Must be 500 odd by now and due to start a new thread!

 

The VF32 and 33 flanges are completely different on the drawings.

I wonder though if the B4 exhaust manifold from the nearside head to the bottom of the uppipe would fit a standard uppipe? The intakes could then be quite easy, wouldn't need them to cross I don't think, and no MAF sensors/pipes in/out etc required. I think the GDB STI intercooler still has two inlets? Conventional downpipes could go in there I expect. What about an oil drain for the nearside turbo?

One of the uppipes (for the secondary turbo) would need a closing flap in it that could be controlled by a PWM solenoid. Presumably you need another flap to stop your primary turbo's boost leaking out the secondary turbo backwards? Unless of course you have the fresh air going through the compressors sequentially? There should be an elegant solution in there that would control smoothly with the minimum of valves.

 

Alan, difficult to estimate figures as always

I think it is over 450 BHP given how it feels compared to previous 434 result.

 

Sounds like you are about to make the ultimate B4

This one is going to be one to sit back and follow with much interest <gets pipe, slippers and ScoobyMag>

 

Would running one turbine or compressor after another be inefficient?

Most of the existing systems seem to work as parallel sequential rather than series sequential. Presumably pulse strength to the second of a pair of series sequential turbines would be poor, as well as restrictive? And a compressor would work at lower PR as the second would be multiplying the absolute pressure put out by the first.

Looks like the BMW setup draws inlet air for the small turbo through the larger one, and there is a flap to stop the small turbo's boost escaping backwards through the larger turbo's compressor. Then there is a flap before the turbines that seems to balance the flow to each one. And I think I see a wastegate on the larger one as well.

 

Have you similar (to BMW) info on the twin turbo 911?