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The mkiv Supra Owners Club

Feck me! (Unexpected BPU)


AlexM

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I'm not sure what you're referring to here. 1.4bar on stock jspec turbos is obviously bad news at any time of the year, and is something I need to rectify. However I don't see that causing my car to end up in a scrap yard (it would be bad for my wallet though :)).

 

Maybe not your car, but your pistons head and valves will be

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Maybe not your car, but your pistons head and valves will be

 

But only in the Winter? :D

 

Why would my pistons/head/valves end up as scrap if a turbo did expire anyhow, due to a rogue turbo blade making its way through the engine or another reason?

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If you drive like that in winter you'll crash (was implied).

 

The implication was purposefully ignored, due to no mention of my driving habits being made in this thread, only the maximum boost I reached at a single point in my journey. Thanks for the explanation though. :)

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Why would my pistons/head/valves end up as scrap if a turbo did expire anyhow, due to a rogue turbo blade making its way through the engine or another reason?

 

My engine digested a turbo the result wasn't pretty. I was lucky that the head could be rebuilt, the rest was scrap.

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But only in the Winter? :D

 

Why would my pistons/head/valves end up as scrap if a turbo did expire anyhow, due to a rogue turbo blade making its way through the engine or another reason?

 

Homer isn't refering to the turbo going. It's the fact that the car will be running very lean at those sorts of boost.

 

I learnt the hard way about turbo'd cars and boost spike and it was a costly lesson at that.

 

Don't drive you car hard again until you can restrict the boost better.

Edited by Matt H (see edit history)
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But only in the Winter? :D

 

Why would my pistons/head/valves end up as scrap if a turbo did expire anyhow, due to a rogue turbo blade making its way through the engine or another reason?

 

You're running too much boost for the fueling. I've seen those levels of boost on my old car and as the 2nd turbo spools it runs horribly lean once past 1.3 bar with 440cc injectors, even with raised fuel pressure.

 

As you don't have an AFR gauge you can't see this happening so should not be pushing the car at all without restriction.

 

It's not even so much the peak boost, it's the speed of the spool thats going to kill it. The stock map just won't supply enough fuel to compensate.

 

THe turbo's are at greater risk as well, but the engine will have shat itself long before that happens

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But only in the Winter? :D

 

Why would my pistons/head/valves end up as scrap if a turbo did expire anyhow, due to a rogue turbo blade making its way through the engine or another reason?

 

Two reasons, 1) Turbos disintegrating and going through the engine and 2) it will be detonating badly due to their being too much boost to fuel which will prob cause damage first than the blades going. The fuel system cant supply enough fuel on a JSpec setup.

 

Get a RR in there before you take it on boost again ;)

 

edit to say Homer got in there first with a better explination ;)

Edited by T2 MSW (see edit history)
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You're running too much boost for the fueling. I've seen those levels of boost on my old car and as the 2nd turbo spools it runs horribly lean once past 1.3 bar with 440cc injectors, even with raised fuel pressure.

 

Got it, thanks Darryl/Matt/Mike. :)

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The 1st cat is very restrictive (the most restrictive of the 2), just removing the 2nd cat will hardly effect the boost.

 

NIc, When you say the first cat do you mean the one closest to the rear of the car or the on closest to the engine (mine has had the one nearest the engine removed)...?

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That's not how it works, BC's don't exactly work on boost, they work on a set actuator adjustment level. When it gets colder this can vary. It's the same reason why you get a variation in peak boost on a car with a restrictior ring when the weather gets colder or warmer.

 

It was explained very well by Ian C (and others) in a thread last year in the tech section.

 

Any idea what to search for to find it? I'm very curious about this. The pressure sensing should remain the same regardless of the temperature. In fact it would be an increase in temperature that would cause more pressure. Colder air means denser air or less volume, not more pressure. If a valve is set to open at 1bar, it will open at 1bar regardless of what temperature it is at. If it is warmer there will be less density of air, if it is cooler there will be more density of air.... thats it though.

 

The only thing I can think of is the components don't react well to colder temperatures.

 

Everyone seems to be disagreeing with me or, in most cases, missing my point and giving random responses. I don't mind people saying I'm wrong but at least read and understand what I am saying and tell me WHY I am wrong.

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Sorry, the way I read it was like the boost controller controls an actuator that comes into play and stops the boost from increasing any more.

To answer your question, you could be boosting to 1.15, add a BC to get it to 1.2 (for no real reason! :D ), then in cold weather it might go up to 1.3 or something.

 

The boost controller does control the actuator :blink: (it just doesn't generate positive boost, it has to be there first)

 

You didn't answer my question though ;)

Edited by Scott (see edit history)
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The boost controller does control the actuator :blink: (it just doesn't generate positive boost, it has to be there first)

 

You didn't answer my question though ;)

 

Hey I never said I knew anything! :D

 

OK, maybe I didn't answer your question, erm...... TBH I thought it was damp air that created more boost and it was just coincidence that it usually happened when it was cold.

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thats what I thought, I have had that removed and Im still only pulling .9 psi at full boost spike (drops to 8/8.5psi )- so I am guessing this means I either have a buggered second cat, a restrictor ring or a very restrictive second cat??

 

Thats interesting as i only have the 2nd cat removed and i hit 0.9-1.0 bar all the time!

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