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

[Poker Face]

I have tried a search but coming up with all sorts in the search.

As per title, rev3 engine, decat upgraded i/c Aem ems 4, 800cc injectors, individual coil packs, 300lph fuel pump. It's going to be mapped listening out for det but I'm aware there are many factors that could be an issue if my memory serves me right from reading various posts over my time on here. The turbo is a gt3076r ( thought I'd bought a 71r so I know it's going to be a bit of lag). I will probably go forged next year so please no telling me to go forged.
As far as I am aware it has a standard mh gasket and is an engine from an st205.

I am thinking map it at 1.2 bar and have ems fuel cut around 1.3 bar.

[bobhatton]

And you have a very good intercooler or big charge cooler I hope

[mrturbotom]

Water meth injection will be a good idea.

1.2bar on a 20b is a whole lot different to a gt30.

I'd start at actuator pressure and keep increasing boost until you're at a decent amount with no signs of unwanted things. Seen 1.5bar ran on a similar setup

[Poker Face]

And you have a very good intercooler or big charge cooler I hope

Did you just answer my question with a question?

We will see when it gets mapped Bob, Its an aftermarket one I bought a few years back(maybe japspeed), ran okay at 17 psi on my CT20. We will be monitoring things closely, you would like him Bob as he leans your way with regards to water injection.

While I remember Bob, you never did explain turbo blankets to me, I ended getting a DEI one anyway.

[Marf]

And you have a very good intercooler or big charge cooler I hope

Did you just answer my question with a question?

Looks like he made a statement to me. The lack of a question mark is what tells me that

He's right though. Some perspective.


1. The stock intercooler is crap. Running stock boost, on a vaguely warm day the stock ECU will pull boost as it detects the intake temp getting too high.

2. My first car was a 1 litre turbocharged Daihatsu Charade. They run 100hp out of the factory. The stock intercooler on the charade is the same size as the MR2 stock cooler


If those two facts don't tell you that you need better cooling when upping the boost, then step away from the engine bay

FWIW I didnt go over 18psi on my MR2 with an ST205 CC fitted. The rev3 CT20 is not very efficient above that anyways

As for your turbo, who knows where the safe limit is really? Assuming you don't get any det and it's mapped properly no reason you couldnt increase the boost, no telling how long it'd last though!

[Poker Face]

Cheers for the input, Marf. I do get where Bob is coming from I was just messing around when i said did you answer a question with a question.
I suppose it depends on how good the Japspeed I/C is. Chris(my mapper) spoken to me about the benifits of a good i/c and keeping an eye on temps. I spoke to him about w/i but he said I should only go down this route if the i/c on it's own is not sufficient. He made some valid points but I'm not going to repeat them and start another w/i debate (plus I'd probably mis-quote him).

The other thing he mentioned to me was the safe limit of power/torque for the pistons but I'm not sure what to expect running the mods I have and only going to 1.2 bar.

p.s i forgot to say I had a Greddy Profec ebc in my first post, so I'll be trying to maintain boost at a max of 1.2bar

[Marf]

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.

[2mad]

Spot on marf .. that's why I've got to check my wideband tuning for a td05

[Poker Face]

You make a very good point Marf. When I first bought the turbo this was what I had in mind and keeping the boost down. I did have an issue with lag and it only went away as boost was turned up. Later on it turned out to be an air leak but I got side tracked from keeping low boost. Prior to what you've said this is what I was thinking.
In my head I have/was thinking 1.2bar or 350bhp whichever the sooner. Obviously there is a bit more to all of this but the idea is to progress towards 350 monitoring knock,inlet temps etc. I know I run the risk of a piston letting go or but I'm willing to try and push a little bit. If all else fails I go forged 6 months earlier than planned and say goodbye to a respray and body kit.

[Poker Face]

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.

Excuse me if I get this slightly wrong Marf but it was explained to me today that 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. The compressor size will affect spool as would the exhaust side have less restriction. This to me means 1.2bar on a larger turbo would be cooler air and therefore better. If this is wrong then someone could they show me a diagram or something.

[C35Rob]

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.

Excuse me if I get this slightly wrong Marf but it was explained to me today that 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. The compressor size will affect spool as would the exhaust side have less restriction. This to me means 1.2bar on a larger turbo would be cooler air and therefore better. If this is wrong then someone could they show me a diagram or something.

yeah, you're both right, sort of

as marf said more cfm from a bigger turbo = bigger bang however that's going to be cooler air going in and it's cyl temps that kill engines.
the bigger turbo will cause much less of a restriction in the exhaust too which in turn will lower cyl tepms (back pressure in exhaust manifold)

cyl pressure doesn't rise in a linear fashion in line with boost pressure either

basically you can debate forever what's the "safe" pressure for x turbo but your engine isn't going to be safe at 1.99 bar and explode at 2.01 bar as some forum types would like to think.. as long as you're not getting det, your AFR's are good, your inlet temps and EGT's are good then you should be fine as long as you're sensible.

its the same as people that say "oooooooh, 320bhp is the limit for stock pistons" (for example) when a power level means absolutely nothing since you can achieve that many different ways be it through cams, head work, boost increase etc.

[Marf]

I may be wrong, perhaps I don't understand turbo compressor maps as well as I thought

[Poker Face]

Thanks Rob, that's an even better explanation than I was given today but along the lines of what you said.
I had a set back today as I took the car in hoping to carry on from the last map to find the calibration was password protected and the person who protected it would not give it to me
So it's off to the aem website for a base cal and start over. Missed my window for this month with my time and the mappers time. At least he spotted some obvious things wrong with the car. Lambda sensor missing and plug dangling,a boost pipe leaking to atmosphere (previously blanked off). So some good came out of today.

[C35Rob]

I may be wrong, perhaps I don't understand turbo compressor maps as well as I thought

comp maps don't have anything to do with how much boost a motor can take though, only if/how efficient a certain compressor wheel is at a desired boost pressure and a given amount of CFM the engine will flow.

[Poker Face]

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.

[2mad]

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

[Ryan S]

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

[2mad]

Yeah im a worrier shep ... ran 1.1bar plus meth no problems .. should be fine doing the same on the gt4.. that's my plan anyway .. my shinny new colder running turbo should help plus massive 4" deep fmic


Us pump gas probably had a major hand in the failures ow and to much booooost


Yeah rereading a few injector fails a few under 15psi fails too .. xxxx happens. Its not putting me off my project

[Ryan S]

it's odd because some of them have done rebuilds and stuff and not upgraded things like injectors and I see little mention of fuel pumps being upgraded too. Most of what's on there seem like botch job builds.I saw one that said "bad tune".......get it done properly then!!!!! it's hard to run lean if you have a wideband gauge as well, and most of them seem to be running lean or getting detonation

[2mad]

Got a wideband , would love det can headphones .. I always try to get the tuning theory right and put it in to practice


I will fpr and neo road tune my car .. then off to the rollers to check for det ... should be fine i hope