NefMoto

Hey guys, I've known about this site for a while but now having to pick a turbo for my STK and my car will be 99% street driven daily driver so I'm looking for the best response and also having built heads so I need top end flow(spinning to 8000 rpms) as well.

Right now I've chosen to go with a BW EFR 7670.  With this turbo I should have full boost(25-30psi) by ~3500-3750 but as the rpms go up and boost holds I'll start to overspin the turbo by ~6000 rpms.  To counteract this I thought I could have the boost taper back to around 18-20 psi by redline and keep the turbo in a safe range.  Is this impossible?  The turbo comes with a boost controller built into the compressor housing but I'm not sure how to link that to the ECU.

The other option I've considered was using the BW EFR 8374 which is basically a step up and I wont have to worry about over spinning but I'll loose about 750-1000 rpms of spool which is not what I'm looking for.

Please dont just tell me to go with the larger turbo because that's not really what I'd like to do....I'd rather have the smaller turbo and hold out 600hp throughout the power band.

Thanks guys!! ;D

Of course, there's numerous ways to limit boost pressure.

Look at LDRLMX in the FR, KFLDHBN allows a max permissible PR by RPM and IAT and is best suited for your needs here.

It is my understanding that the integrated boost control valve can be controlled the same as the N75, but I can't confirm that.

Thanks for your response and I'm not sure what the second section of your response is referring to(looks like I've got some research on my hands to do) but from what I can tell the n75 has a two wire plug just like the built in ebc on the turbo.  It looks like it might also be a good idea to add a speed sensor to the turbo to make sure I dont over spin it.  Has anyone ever tried anythnig like this?

25-30psi at that RPM?  How did you come up with such a figure?

I'll believe it when I see it, I think you would be lucky to make 20 psi by that RPM.  Are us using a kit? or making your own manifolds?

Bigger turbo = Better  :P

EFR solenoid is PnP in ME7 harness'

25psi by 3500 and 30psi by 3750-4000.  Here's a precision 5858 for comaprison(has a slightly larger compressor wheel inducer and a heavier turbine wheel(more inertia).
He also has boost rising were I will be tapering(due to overspinning and power will fall off if overspun as he did)
(http://i1091.photobucket.com/albums/i385/JMont23/Boostcomparegraph_zpse0286a95.jpg)

I have a friend making a manifold for me

No, bigger turbo= more lag which is not good for street driving

;D ;D ;D ;D ;D ;D ;D

I find that graph hard to believe... but I'll wait to see your results.

FWIW, here is also a graph of a PTE5858 on an S4:

(http://i1091.photobucket.com/albums/i385/JMont23/BoostProfile5858_zps0fa23331.jpg)

This one isnt that bad....could have to do with exhaust housing, restrictive stock heads, gas, ect....

I just re-read the graph you posted... 25psi happens AFTER 4500 RPM.

I think you're mixing up desired vs actual boost on that graph.

No, i saw that too but that is with the 5858(less advanced turbo), on stock IM, heads, TB, 93.

I have +1 valves, RS4 IM and TB, better turbo, more efficient IC, I expect better spool.

You will gain some spool, but I would not expect 1000RPM gain in spool.

The spool will actually be delayed with bigger intake tract. I see that happening on my new intake setup, RS4 intake, etc, etc. Remember, small port/intake promotes faster spool/more pressure in low/mid range but chokes in higher RPMs.

Speaking of intake restrictions, remember that spool vs RPM means nothing if RPM rises slower vs time :)

True I suppose, but with the right combo (even with bigger ports/runners, etc all around) it is possible to have a sorted setup that will spool earlier.

Of course if you're just optimizing the intake side (RS4 manifold/TB) then you just have more volume to fill.

Either way, I think 25 psi @ 3500 & 30 psi @ 3800 is a very lofty proposition.

I think lofty is putting it nicely. I'd say out of your mind.

Cool, looks like you have this all figured out then.  Seems Like this post and your question is pretty pointless if you don't want the advice of people with single turbo B5 S4s.

Haha... ok.   I've only seen one person comment about running a bigger turbo and there was no reasoning behind it.

I'll also be running a twin scroll turbo with a twin scroll manifold which should also help spool at least 200-300 rpms. 

My primary reason for this thread was to ensure I could taper boost in the upper RPMS so I dont overspin the turbo and hopefully with the boost controller built into the turbo(which I've read I can ;D)

I think I will go ahead and get a turbo speed sensor as well to know what the tuurbo's doing in the upper RPMs.  Can I also run the turbo speed sensor through the ECU or will I need a guage or something?  I'd like to see the digital output if possible on my computer :P

OK I'm going to post it here even though I posted it on AZ I'll post it all here so everyone sees it.
I've tuned quite a few single turbo setups now - 5858, 6262, 6266, S256, AGP 3.2, 6766 so I can tell you 100% the pros and cons of all the setups.

You can taper the boost down all you want as you head to redline but you will NOT get what you want.
The 5858 was NOT overspinning... this is evidenced by the many many (read 50+) variations I tried of boost vs timing.
Tapering the boost up approaching redline as the engine got away from the knock limit at higher rpm increased power. The 5858 simply does not flow enough air to behave as you desire.

Check this out - 5858 and 6262 on Montys car and the 6766 on my car. All on pump gas and meth:

(http://i1357.photobucket.com/albums/q755/britishturbo/5858vs6262vs6766-pump_zpse868b895.jpg) (http://s1357.photobucket.com/user/britishturbo/media/5858vs6262vs6766-pump_zpse868b895.jpg.html)

Pretty cool huh?

The following is very neat, it shows the 5858 and 6262 on Montys car and Celisons FT21 frankenturbos.
This tells you a lot right here:

(http://i1357.photobucket.com/albums/q755/britishturbo/5858_stk-vs-ft21_zps623dd06c.png) (http://s1357.photobucket.com/user/britishturbo/media/5858_stk-vs-ft21_zps623dd06c.png.html)

Again it all depends on what you want to do with the car.
If you spend 90% of your time in traffic or around town then yes a 5858 sized turbo is right for you.
If you do a lot of highway racing and spin to redline a lot then you want something bigger like a 6262 or 6266 sized turbo.
Or if you are crazy like me go with a 6466 or 6766 lol.

Turbo sizing is always a compromise. Always.

Oh and yes a 5858 will hit 25psi at 4000rpm on a 2.7 with stock top end.

And just for the fun of it... here's a comparison of an E85 Frankenturbo car vs my car running E85 with the 6766 and the nitrous antilag on lol.
I think you can guess which is which ;-)

(http://i1357.photobucket.com/albums/q755/britishturbo/bt-vs-rob_zps51f223dc.png) (http://s1357.photobucket.com/user/britishturbo/media/bt-vs-rob_zps51f223dc.png.html)

Let me know if there is any specific turbos you would like to see compared... I have many many logs of them all.

I really think the best thing for me to do would be to go for a ride/drive in these cars to really understand what I liked/wanted.  You guys should plan a drive down here haha 8)

Where are you located?
On August 11th I'm hosting another Audi meet in State College PA, will be many different cars there.

If the controller for your speed sensor can output 0-5v analog signal it can be wired into one of two rear o2 sensors and therefore made avilable as a variable in Me7 Logger. Read thread about hooking up zeitronix/WB o2 into stock ECU to give you an idea.

Charlotte, NC  :'(

I don't know why all these people are saying you can't spool the turbo that fast,
nitrous can spool huge turbos really fast look at what the supra, and honda guys do.
 :D :D :D :D
I once put a gt30 something on a VW ABA 4 cyl ran standalone and TDI gears with a vr ring and pinion.
Ended up using a 100 shot to spool it, made 390 something wheel with 8v.

This. Decide what you really want, THEN pick the suitable hardware.  Too often people have ideals about their hypothetical perfect 'happy medium' turbo and forget about the physics/trade-off.  There's always a trade-off, you've just got to decide exactly where on that spectrum your preference lies.

Nitrous is totally unreasonable for a street car... not to mention it gets expensive.  For a drag car sure (if your class allows it) why not.

It's far more important to build a proper and efficient setup then use a bandaid like Nitrous IMO.

I was simple pointing out that it helps big turbos spool. With turbos it is very difficult to have your cake and eat it too.
If you get a big turbo your going to wait for it. Things like proper tuning and very well disigned manifolds can help with
boost. At the end of the day big turbos equal longer spool times but most of them make up for it with the sit of the pants
pull you only get after waiting for boost to build in a 3 gear pull from like 25mph. ;D
I was just bringing another idea to the table. Spool time is something that does not bother me to much I pick a turbo that makes
the power I want at the boost pressure I want to make it at, then figure the rest out later.