[Mk2] [Turbo] Stock internals safe (ish) level of boost

[C35Rob]

I found this using Google, maybe learn from others mistakes or just make them again.


http://66.49.162.16/howtoblowyourengine.html

The guy who blew his engine at 1.3bar was using a CT20b not sure what ic etc he had.

That is horrifying .. really worried about the life expectancy of my stock 3sgte motor now .. turn boost up n takes ya chances

have you read those failures properly??

These folk are idiots, 91 octane fuel, 20psi. I mean c'mon, that's just asking for trouble

MON/AKIvsRON it's a yank site, their 91 is the equivalent to 95 RON over here, their 93 is the equivalent of 97 RON

[Ryan S]

so 95 octane at 20psi is OK?? on 540s as well!!

[2mad]

You cant boost a car in anger on 95ron ... Can you


Edit .. sheppy beat me to it lol .

[Ryan S]

You cant boost a car in anger on 95ron ... Can you

I believe 95 RON is what the cheap stuff here is, I may be wrong as I never use it
Although on the other hand, i've just realised that the American mr2 tubby was actually for the american market, so I would assume the cars ecu would be designed to use their crap fuel, doesn't bode well for running higher boost though.

[2mad]

You cant boost a car in anger on 95ron ... Can you

I believe 95 RON is what the cheap stuff here is, I may be wrong as I never use it

Me nether .. i like my engine

[Poker Face]

I've seen knock detection kits for £320 on Efi parts in Runcorn . He's the guy who will be mapping my car.

[2mad]

I'm on a shoe string tuning my car .. road tune I can do .. then off to the rollers to check I got it right ..


Ps .. I tried making diy det cans .. didnt go well lol

[bobhatton]

The problem in determining a safe boost level comes because you are not running the stock turbo.

The stock turbo will flow x lb/min of air at 1.2bar

A gt3076r will flow higher than x lb/min of air at 1.2bar.

More air, more fuel, bigger bang in the cylinder. You're in uncharted waters really, even at 1.2 bar.

You are 100% correct with that statement.

It is the total weight of air that gives the power output and has nothing to to with boost pressure.

[bobhatton]

the size of the turbo/ compressor has nothing to do with airflow per say as 1.2bar is measured at the manifold and that would be the same for any turbo.

That is completely wrong.

To work out the total weight of air flow into an engine the pressure AND temperature has to be known.


1 bar at say 100c will be so much less weight of air than 1 bar at 50c

Every engine needs a design, once that has been completed the air flow will be known and the correct compressor chosen with the help of the compressor maps, that is what they are there for.

[C35Rob]

so 95 octane at 20psi is OK?? on 540s as well!!

absolutely not on a standard ECU, I never said that. just making sure we're all singing off the same hymn sheet as lots of people aren't aware of the difference

[Poker Face]

A larger turbo will be more efficient and therefore have a lower temp so there would effectively be more air at the same level of boost than a smaller turbo?

[2mad]

A larger turbo will be more efficient and therefore have a lower temp so there would effectively be more air at the same level of boost than a smaller turbo?

That's what I've been lead to believe .. Hoping the td05 will do this .. extra bhp, same boost level . ow and better flowing turbine , get those exhaust gases out more efficiently.

[C35Rob]

A larger turbo will be more efficient and therefore have a lower temp so there would effectively be more air at the same level of boost than a smaller turbo?

yes.

think of two desk fans running at the same speed, one is bigger than the other. big fan pushes much more air than small fan. to get the same amount of air from the small fan you need to turn it up to a higher speed.

[Ryan S]

so 95 octane at 20psi is OK?? on 540s as well!!

absolutely not on a standard ECU, I never said that. just making sure we're all singing off the same hymn sheet as lots of people aren't aware of the difference

Haha, some of those failures are moronic, it seems the last thing the yanks want to do is change the pistons!

[Poker Face]

The car is being mapped this week and has been encounering det anything above 1.1bar getting 281hp. Im not sure what temps its been running at etc and will hopefully get more info later. Its a lot better than the 220hp from a previous cal(which was locked) running at 1.2Bar.
From the quick email late last night it sounded like he thought there was some back pressure or the compression ratio is too high.
I'm not sure what brand of aftermarket exhaust I have but it shouldn't be restrictive. I/C is a Jap speed. Thats all I have time to post at the moment but any thoughts please?

[Poker Face]

Just had an email from my mapper, inlet temp was low 30 's indicated but thought it felt hotter. Ic cooling fan had failed but even after repair those were the temps. Next time we're going to put some K type thermocouples on and a data logger and see what the temps really are. I'm thinking new ic a greddy/trust or maybe a cc.

I'll probably leave it until after summer and go forged low comp ratio pistons and leave the respray til next year.