Thinking out loud

[2wd_Sled_Puller]

If the stock VVT turbo doesnt run out of effenicy until 45 psi of boost why do people talk about them letting go at 32 psi. Ive been thinking about bumping mine up from 42 to 45 but i am going to keep it how it is until i get the funds to replace it then play. I have had good luck at 42 psi. I just wish it wasnt so danm laggy. So whats killing these chargers

 

[LarryJewell]

too much boost for a stocker turbo

 

[TYREBOYZ_DEMAXIN]

if you do push the turbo that high reinforce the boot on the intercooler driverside on the bottom because it will come off..not sure why the LLY has thatproblem.

 

[Killerbee]

Are you reading from a gauge? I suspect you are reading MAP from the bus. In that case 42 psi (absolute), is 28-29 psi of boost.

The stock turbo won't easily get to 42 psi of boost, those that have, don't own them long.

 

[MMLMM]

My old VVT on my LMM would see a 45psi spike and maintain 40-43psi right after the 1058 went in. I ended up having to run efi to calm that sucker down.

 

[Killerbee]

I think you guys are confusing terms. MAP is not boost. Frequently, scanners will label MAP as boost, and it is confusing. A stock LLY (OP) induction system won't last a minute at that level of gauge boost, IIRC.

 

[MMLMM]

I think you guys are confusing terms. MAP is not boost. Frequently, scanners will label MAP as boost, and it is confusing. A stock LLY (OP) induction system won't last a minute at that level of gauge boost, IIRC.

My gauge is reading correct boost. Im not reading from a programmer.

 

[Killerbee]

The LMM has less hardware challenge, and frankly I haven't tested one.

Are you commanding over 55 psi of MAP through programming? If not, I am going to say, you either have a bad gauge, or a bad MAP sensor. Maybe I am wrong.

 

[MMLMM]

The LMM has less hardware challenge, and frankly I haven't tested one.

Are you commanding over 55 psi of MAP through programming? If not, I am going to say, you either have a bad gauge, or a bad MAP sensor. Maybe I am wrong.

No I was running a canned tunner cranked up, boost was perfect 30-32 and 35 max, then did the trans and a 1058 and it was at that minute it would run that much boost. I tried my other programmer (same brand) and it did the same. Boost gauge is fine, MAP is fine. Once I went with efi, the tuning was able to bring the boost levels under control.

Either way I knew 40-45psi would not be good on that turbo, I only ran around like that baby footing it for no more than a week though.

 

[Killerbee]

I am clueless why changing a tranny would overboost the motor.

Must be some mystery here. Or maybe someone can shed some light on it.

Do EFI (bus) and your gauge agree, after correcting for baro.?

 

[MMLMM]

I am clueless why changing a tranny would overboost the motor.

Must be some mystery here. Or maybe someone can shed some light on it.

Do EFI (bus) and your gauge agree, after correcting for baro.?

I think it was the converter allowing it to spike that high over factory converter. At the time everything seemed to agree. I know the gauge works right I'm still using it. However Im not running a stock turbo anymore.

Also Im positive it was mostly in the tuning. My sisters truck spikes a little higher now after a 1058 but it doesnt go crazy and my guess is the big ass tires shes running.

 

[Brayden]

Load.. Once you get a more efficient converter the engine can load down harder.

I agree though, stocker is no good for you above 32 or so. Watch the drive pressure it is up there! And for a stocker to move 45psi worth of air it has to be in orbit. And the thrust bearings won't take that. They'll give up on you in a hurry.

Brayden

 

[malibu795]

ok... form the map that MDE posted of the LLY charger.. the map went to ~4:1 or 60psi

max flow was about 40-45psi..

i have seen the map for the IHI and is 31-32psi si the max at max flow IAW the map chart.


how many stock LLY have over spun?

60 MAP psi (45psi) would be the max i would run acording to the comperssor map that MDE posted

 

[Killerbee]

60 MAP psi (45psi) would be the max i would run acording to the comperssor map that MDE posted

This would take pages of explanation, but you are using PR assuming that there are no losses on the intake side, CIP or the output side, COP.

If that is the case, and you are at sea level, then you would have a good point.

In reality this is not the case. The LLY intake loses are 4-5 psi with stock airflow, up to 9-10 psi with higher airflow numbers. This effectively reduces CIP. Add some altitude and it worstens. Denver is around 12 psia. Add them together, and you get a CIP of around 8 psia stock, and 5 psia with augmented boost. That number goes in the denominator. In the numerator, COP, plumbing losses must be added, around 2-3 psi for stock flow, 4-5 psi for augmented flow:

PR=COP/CIP

Now, it can't even be plotted on the referenced map page , there isn't enough vertical scaling. For 30 psi boost, up in Denver:

PR=(30+12+4)/(12-7) = 9.2 (LLY only)

There is your destroyed turbo. There is the cause of LLY overheating also.

 

[2wd_Sled_Puller]

Are you reading from a gauge? .

Yes i know its hard to beilve it pulling 42 on a stock VVT but i have put more then 1 gauge in it and they all read the same. So i dont guess its that. I got it plug right into my intercooler

 

[Killerbee]

I have seen damaged MAP sensors. If yours reads low, the PCM will try to compensate and overboost to satisfy the call. It does make a case for a separate gauge