need quick advice on a possible single-buy

[Clarkey]

my guess its going to be 1.2-1.4 bar max.

 

The GT42 is big turbo Jurgen. If I have to raise my fuel pressure to run that boost pressure on my 550's ... on 440's .. it'll kill the engine.

[Clarkey]

It's not about twisting it and a bun fight. You said that Alex's figure was incorrect. Alex quoted that figure because of the insufficient fueling on those 440's. You said :

 

Mine was running 440's and had 395 at the hubs so to say a car can only run 420 brake on 440's is total bollox.

 

Alex said that figure he mentioned - BECAUSE OF THE LIMITATION OF ASSUMED 440's WITH A SINGLE TURBO CAR! So, you saying what Alex said was crap - is total crap!

 

What apart of that didn't you understand ?

[Jurgen-Jm-Imports]

The GT42 is big turbo Jurgen. If I have to raise my fuel pressure to run that boost pressure on my 550's ... on 440's .. it'll kill the engine.

 

i have not read the full thread lol but surely this car can run safely at 1.2 bar or even 1.4 ?? or is this too much for this turbo with stock injectors, i would be interested to know just for future ref.

[Clarkey]

i have not read the full thread lol but surely this car can run safely at 1.2 bar or even 1.4 ?? or is this too much for this turbo with stock injectors, i would be interested to know just for future ref.

 

Well, if my duty cycle is skyrockets at 1.4 bar with 550's - running a BL T61 (smaller than than GT42) - imagine what the DC is going to be like on 440's ?

 

Because my DC is WAY too high @ 1.4 - that is the reason why I keep the boost to 1.1 to 1.2 bar .. because then the DC is 80 - 85%. I've been recommended to keep the DC below 90% - so I've got plenty of slack DC .. if for example:

 

a) Cold morning

b) Cold Morning = Cold Air

c) Denser Air without increasing boost going into the intake

d) Denser Air = Need more fuel to burn the air off

e) More Fuel = Increases DC. Increased power above normal ambient temps.

f) Increased DC because of Cold Air = I have 15% slack .. so, I shouldn't hit 100% duty.

 

To give me more DC - I would only need to raise my fuel pressure .. and have my EM map tweaked.

[RobSheffield]

i have not read the full thread lol but surely this car can run safely at 1.2 bar or even 1.4 ?? or is this too much for this turbo with stock injectors, i would be interested to know just for future ref.

 

'Safely' here is the key Jurgen!

 

It is being argued back and forth, stay tuned, an answer will arrive in a few days

[Jurgen-Jm-Imports]

'Safely' here is the key Jurgen!

 

It is being argued back and forth, stay tuned, an answer will arrive in a few days

 

oh well there we go then

[dangerous brain]

Right so there ya go, shot straight in the foot then, the assumed limitation of 440cc injectors in the real world not the one according to clarkey is actually 440bhp. I gave an example of a car proving that more than 420 bhp is achievable on 440 cc injectors, in fact in the bit you just quoted, so if understanding is the issue here perhaps you are bit lacking.

 

For the hard of hearing Alex's quote of 420 bhp with 440 cc injectors is not achievable is not exactly true and I can prove it. Do I need to make it any clearer?

[Clarkey]

You're talking about a stock twin car. This is a SINGLE car .. what Alex said was applying to a SINGLE car on 440's.

[dangerous brain]

i have not read the full thread lol but surely this car can run safely at 1.2 bar or even 1.4 ?? or is this too much for this turbo with stock injectors, i would be interested to know just for future ref.

 

Thats just it at 1.2 bar the stock injectors wont cope with the airflow and will run lean, very lean would be my guess. If its run at 0.7-0.9 bar it will still run lean but maybe not lean enough to cause damage.

[Homer]

Jurgen, some of the lads know what they're talking about

 

For example, my T67 could not even run 0.8 bar on 440cc as the injectors would be pushed past their limit.

[dangerous brain]

You're talking about a stock twin car. This is a SINGLE car .. what Alex said was applying to a SINGLE car on 440's.

 

It doesn't sodding matter if its single or twin. 420 bhp is 420 bhp. It doesn't matter if that 420 bhp comes from an NA V 12 or a turbo'd up 2 litre. 420 is 420 period.

[Clarkey]

my T67 could not even run 0.8 bar on 440cc as the injectors would be pushed past their limit.

 

And is a GT42 bigger or smaller than a BL T67 ? And how would a GT42 at WG boost (0.7-0.8) bar effect the duty cycle at stock FP 36psi on stock 440's ?

 

(The FP is again assumed because it has no other mods except the blower)

[Clarkey]

It doesn't sodding matter if its single or twin.

 

So, a T61 is the same as stock ceramics ? What you've just said there - a blower is a blower right ?

 

Doesn't matter what type of turbo you bolt on ? If the car is fine at 0.8 bar on stockers .. then it's reasonable to assume it'll be just as fine with a GT42 ?

[dangerous brain]

Nope because obviously a gt42 at 0.8 bar is gonna produce more power than stock ceramics, wether it produces more than 420 bhp or not I'll be honest and say I don't know, personally i wouldn't have said so if everything else was stock, exhaust, intercooler, cats etc but thats just a supposition on my part. My comment was that 420 bhp is available on 440 cc injectors. A blower clearly isn't just a blower but a power figure is definitely a power figure regardless of the means of achieving it.

I've also said that the only way to really be sure about the car in question is to check it. In the UK I'd say for sure forget it as there are enough cars to be able to pick and choose and investigation isn't worth the money. That is not the case in Sweden and if the car is a bargain (considering cars are ridiculously expensive there) its worth a bit of investigation.

[Clarkey]

DB. What started this off was - & This was my whole point and where I am disagreeing with you. (Just to clarify I'm not talking about your power figures .. that's something you and Homer were talking about)

 

You said Alex's figure of 420BHP was incorrect. In later posts you said:

 

If it's only got 440cc injectors it's limited to about 420BHP. which is completely not true. If you wanna be really picky the accepted rule of thumb is a cc for bhp is the limit ie 440cc injectors will support 440 bhp

 

You're talking about a stock twin car. This is a SINGLE car .. what Alex said was applying to a SINGLE car on 440's.

 

It doesn't sodding matter if its single or twin.

 

Now, Alex's figure of 420BHP is based upon a single turbo car. The car is nolonger a stock car. Thereby - the fueling requirements are now completely different.

 

The reason why the 420BHP figure was made - was because the 440 injectors won't be able to support any more additional power for a SINGLE TURBO. Because they are insufficient.

 

The 440 injectors are insufficient - because that GT42 is now shifting alot more volume of air than the standard ceramics. Because it's got more AIR - it needs more fuel. To get more fuel - you need to fit bigger injectors.

 

Infact, Ian C has even said in his posts - that the midrange will be very poor/lean. Which is an indication that using 440 injectors on a GT42 - is an insufficient fueling setup.

 

the car has been runing 0.7 with the current setup

 

I wouldn't be too sure about that though chap as looking at the spec in the ad its saying that theres a blitz nurspec, and 3 " cat replacement pipe on there. Without any other boost control and assuming its J-spec it won't hold at 0.7 bar. Maybe its got a restrictor fitted in the exhaust to prevent boost coming up

 

That's what "something" called a Wastegate spring is for. It's fitted to the External WG to control boost. Have a read of Terry's post. Singles don't use the restrictor ring fitted in the exhaust. It doesn't need it! So yes, providing the WG spring is properly sized to 0.7 bar .. then it will hold around that pressure. It may have a tendancy to over-boost perhaps to 0.8.

 

I've got a 1bar WG spring. And sometimes with the EBC off - I see 1.1 Bar.

[dangerous brain]

OK being of more reasonable mindset this morning I'll ask a couple of questions.

 

First up does the boost pressure on a single affect the power output of the car? So far I've been under the impression that a single turbo could produce the same results as a stock twin setup at a far lower pressure. So to produce say 420 bhp a single will only have to put out for instance 0.7-0.9 bar?

 

If thats right and the engine is only flowing 0.7 bar why would the AFR's be different to an engine flowing 1.2 bar on stockers putting out the same power? I'm making an assumption that the airflow sensor will count how much air has gone past and into the engine and attempt to stick the right amount of fuel in.

 

Second question is this, why will a single turbo not run away with its pressure? Will it be because the waste gate has to be replaced as part of the conversion ie the stock one could not be still there? I only ask as mine used to run away to 1.5 bar which is the known thing with J-specsand the only way to stop it was with a restrictor ring, and if the waste gate was left stock with no boost control mods wouldn't it still do the same thing?

 

I agree that the fuelling of this car isn't right and needs upgrading to see its potential. I also agree that leaving it as is will ultimately see the engines demise. What I was attempting to say albeit a tad wrongly is that the engine isn't necesarily shot to crap just yet if its been kept boosting low and has only done 3k km it may be OK. A compression test and pulling the plugs will tell this straight away won't it?

 

I apologise for my bolshy attitude last night btw

[Tom S]

Nice Read.

 

Hi all.

[csa]

The var IS running 0.7 bar with 3 inch dp and 200 cells race kats, by statement of the owner the wg ring is limiting this boost.

 

also it IS running stock 440's

[Clarkey]

If thats right and the engine is only flowing 0.7 bar why would the AFR's be different to an engine flowing 1.2 bar on stockers putting out the same power? I'm making an assumption that the airflow sensor will count how much air has gone past and into the engine and attempt to stick the right amount of fuel in.

 

The GT42 being bigger than standard ceramics. At less boost pressure - the volume of air going in is greater. A practical example is Affennel's car has a BL T61 fitted.

 

He still had his 440's. When he BPU - he was boosting to 1.2 bar. When he got his single fitted he was boosting to 0.8 bar on the T61. He got a Aero FPR fitted to crank his FP up - to give him more DC. So, making his 440's act like 550's.

 

Otherwise his AFRs would be lean ... because his T61 is shoving more volume of air in.

 

Homer has already said that with his T67 he couldn't run 0.8 bar on 440's.

 

That's my understanding from talking to the techie people here. Now, if I'm wrong - I'll put up my hands and post up.

 

Second question is this, why will a single turbo not run away with its pressure? Will it be because the waste gate has to be replaced as part of the conversion ie the stock one could not be still there? I only ask as mine used to run away to 1.5 bar which is the known thing with J-specsand the only way to stop it was with a restrictor ring, and if the waste gate was left stock with no boost control mods wouldn't it still do the same thing?

 

Singles have external wastegates - your BPU car had it's wastegate inside tubbies - which as you know is easily overwhelmed and needs a restrictor. On a single, minimum boost is controlled by the wastegate spring. It acts as the restrictor ring.

[Miguel]

 

 

 

Second question is this, why will a single turbo not run away with its pressure? Will it be because the waste gate has to be replaced as part of the conversion ie the stock one could not be still there? I only ask as mine used to run away to 1.5 bar which is the known thing with J-specsand the only way to stop it was with a restrictor ring, and if the waste gate was left stock with no boost control mods wouldn't it still do the same thing?

 

 

With a Single trubo converstion none of the stock boost control set up is there. On the stocks you have an internal wastgate and on Jspecs the appature of this gate is not large enough to release gasses at higher boosts hence boost spikes and using a restrictor ring.

 

On a single you replace the whole system and it uses a much much larger external wastgate of which its boost release threshold is guvorned by the WG spring. Once the boost pressure matches the Spring rate the gate opens to release exhaust gases bypassing the hot side blades of the turbo and therefore limiting boost. These systems , although can still spike, are much much less likely too than the Jspec stock set up. That's where the term "running of WG comes from" as you are just using good old mechanical boost control, if you want to raise it you use a boost controler or get a higer rated WG spring:)

[RobSheffield]

How does a BC increase the boost then? does it just 'bleed' air away from something and fool the WG?

 

Say if you were running 1.6 bar on a single

[Miguel]

Yup BC just bleed boost reference pressure away from the wastegate until it hits the user defined setting and close the bleed circuit so the gate activates again. And depending on how you plumb the BC in they can also add boosted pressure to the back of the gate to help hold it shut.

[dangerous brain]

What I am not understanding is the volume of air shifting in at say 0.8 bar on a single is similar to that of 1.2 bar on stockers. So is the air volume sensor ie MAP or MAF sensor not measuring the quantity of air correctly. My understanding of fuel injection is the air volume meter figures out how much air there is and the ecu then tells the injectors how much fuel to let in. If it see's 420 horses worth of air be that forced induction or not surely it'll put 420 horses of fuel in up to the injectors actual maximum flow rate. That was why I understood that my car outputted the increased power it did without the requirement of a piggy back ECU.

The thing I can't get my head round is in principal the amount of air throughput for a set amount of power should be the same shouldn't it? And if you put 420's worth of air through no matter how much air that is and how it gets there shouldn't the airflow sensor figure that out and put the required amount of fuel in??

[Miguel]

I think that is where you are getting confused. MAP sensors measure Pressure not volume. And MAF meassure Air flow.

 

Bigger turbos can physicaly mover more volumes of air at lower pressures thats where things go awkward.

 

Let's put it this way you can fit a fag packet inside the apperture of a gt42, I would not want one running 440's on that turbo. If you can afford to slap a Gt42 on a car you can afford to finish the job . Having a turbo of that size and only using it @.7 bar is just a total waste of a turbo.

[dangerous brain]

Right so a J-spec is MAP right? So in the least it would need a MAF? Now I can see why it would run lean if it was putting in 0.8 bar of fuel but there was equivlent of 1.2 bar of air in there. The fog is lifting