What is the S5 turbo's redline? We are trying to figure out why it is bad to run 20 PSi on it based on what I have read about out engines and the compressor map that REted told me was similar to the stock HT18.

Does anyone know its redline? At 20PSI its ~103,000rpms



Santiago

 

THis is what we have come up with so far.


Santiago


PS- Props to Andrew for this pic. And To REted for the info on this compressor map.

 

I don't know the exact number, but it's the bearings and seals that govern the max safe rpm. It's nothing to do with the compressor or it's map.

 

I udnerstand that it has nothing to do with the map but I thought someone would like to see it. We are trying to figure out why it is bad to run such a high PSI on the stock turbo. NOTE>> THIS IS NOT MY IDEA I AM HELPING A FRIEND WITH HIS QUESTIONS ABOUT THE STOCK TURBO. We ran the numbers and plotted the points on the compressor map and we came up with decent efficiency numbers given our base number for lbs/min(we used 30) and the only thing I could THINK of was over spinning the stock turbo.

Santiago

 

Here is a graph I have complied using help from Santiago and information from his friend saying anything above 14PSI is above the redline. Everything outside the dotted box is a safe place to run the turbo, at least from my understanding.

 

um well try it. i dont know if the stock turbo will be able to make that kind of boost, i mean it drops off like crazy near redline.

 

He is going to use an MBC for this most likely. He is going to do some fuel mods first though.

 

The dotted lines you've drawn relate only to boost. Shaft rpm is the curved lines running up the map (84200, 96600, 106000, etc), so your "safe" area doesn't relate to the turbos "redline" at all.

Also, you can't assume an airflow number. You have to actually measure it and see where you are on the map. The airflow you get at a certain boost depends on many different factors, including most obviously, the engine that the turbo's attached to and how free-flowing the exhaust and intake are. A modified engine will have greater airflow than a stock one at the same boost.

The only people who could give you a definitive answer on the turbo's shaft redline would be the people who make and/or supply the turbo's internal components. A turbo workshop would be able to give you an educated guess. The figures that pop up on forums are based on anecdotal evidence gathered by many people (i.e. reporting what boost the turbo popped at).

 

I compretly forgot about RPMs being the curved lines. Let me fix Andrews pic.


Ok I added a grey line to the general RPM curve at which the turbo will over spin itself.

 

Updated. Thanks NZ. I wasnt totally sure about it, which is why I posted it here. I hope this is correct.

By the way, if anyone doesent understand these graphs, everything above the black line with arrows branching off is an unsafe PSI to run, and everything below is 'safe'. But, like NZ said, this changes between cars depending on mods.

Correct?

*crosses fingers*

 

My theory on not to spin the stock turbo over 15psi is because of the carbon (front) seal on the compressor backing plate.

Everytime I tried to run over 15psi, the carbon seal promptly ate itself to pieces in a week.


-Ted

 

Hopefully this will convince other people why I told them it wasn't good to run over 15 PSI.

Santiago


PS- If anyone wants to comment/argue lets have it.

 

Oops...

 

After some work me and andrew edited An article I read about compressor maps. This will hopefully help educate some of us that are new to this kind of information.

Here is the link How to read Compressor Maps


Enjoy!


Santiago

PS- Credit goes to Andrew for coding this into HTML

 

Bump for the people that were looking for this with the plots for boost.

 

now i know how to read a compressor map. hooked on 1987rx7guy works for me

 

great so we all want to run about 13psi is what that plot says it looks like the efficiency starts to fall off horribly at 14.

good work guys. i'm impressed.

 

i THINK 8200RPM

 

I think you need to read the thread before you post...

 

Bump for some friends that wanted to see this.

 

Damn dude! Good job

James

 

Thanks James...


Now I want to pose a question about the stock turbo's compressor. Is it at all possible to upgrade the bearing on it? Also a lot of the boost drop-off is likely due to the turbine side of the unit has there been anyone that has tried to work with and modify this or use a different turbine wheel with the stock housing?


Santiago