Duke

Hotside sizing is also about powerband and top/bottom end power, not only EGT.

Dark Lightning

This is one of those double-edged swords. Pick your poison:

If you want instant power but not as much peak power, you want a smaller AR.
If you want peak power but you're willing to wait for it, you want a larger AR.

Smaller AR = faster spool + more likely to experience high RPM boost fall-off.
Larger AR = slower spool + less high RPM boost fall-off.

[edit]

We agree.

Corleone

According once again to my friend "Nille" he says that its about 500 rpm difference betwen .6>.8 and it spools a little slower of course. For 400 rwhp it takes about 1,25 bar (18psi) and 7000 rpm or 1,45 bar (21 psi) and 6500 rpm. Of course with a good VE, head, cam, exhasut, IC and so on.

Corleone

Of course. What I mean with egt is that is a big criterium if you want to have max power without having bigger hotside than neccecary. When the egt rices from the max of 900-950 degrees C there is nothing to do. You can go a little richer but it will not help much. You have reach the potention of the hotside.

My friend dynoed a 1,8 liter Nissan and they come to 460 hp, no matter what the increased boost up to there was no moore, then they changed from a .82 A/R to 1,0x A/R and with the same compressor they reached 580 hp.

I have a spoolup thats ok but if the car should be fast I have to gear down so I have 4 k rpm, from there I have full boost in notime. Today I have tuned my ignition a bit and now I reached 20 psi at 32-3300 rpm staring at 3:rd gear and 1500 rpm. The car is of course not so fast anyway with that boost at that rev, you need to come up to 4 k to take advantage of the head, cam and so and the higher VE.

J Chen

Hey Duke,
You using a Reliaboost/Accuboost ?
If not try it, spool comes up much
faster. Also upgrade your wastgate
& you'll be smiling.

Duke

Corleone what's the stated powerband for that Milledge-cam?
I'm very impressed with 20 psi at that rpm if the torque curve carries on (not taking a steep dive) to 7000rpm. 3000rpm powerband at full boost in a 400rwhp 951 is nice!

J Chen>> yes a Tial is on top of my mod list together with a good simple EBC like the PRofecB. Hopefully it will make wonders Especially at higher rpm's since my current WG can't hold more than around 16 psi.

J Chen

Hi Corleone,
Whao, 20 psi at 3200-3300 rpm ? Hope that
after my tuning I can get better spool up
with my GT25. Are you running an EBC ?
In reality, boost is a by product of back pressure.
It simply means that the engine cannot consume
all the air that the turbo is providing. A better
indication would be what hp & torque is available
at that rpm regardless of the boost pressure. To
me the ideal situation would be to get maximum
hp & torque without resorting to the use of high
high boost. Would you agree Corleone ?

Pauerman

Just a side note about the Accuboost MBC - my personal experience with this controller in my '86 car is that it will not maintain the same set boost pressure in each gear. This is with a TiAL 38mm plumbed in single port mode. I don't know if this fluctuation is inherent to MBC's in general, but coming from an EBC (Profec B) in my '89 car, I can say that EBC's are the way to go if you're looking for accurate boost settings in every gear.

Just my .02 cents

J Chen

Yes, no MBC can do that. I guess that's
the advantage of going EBC. BTW how
reliable is an EBC ? I for one do not like
to have too many gagets in my car. I
remember Myswiss posted a thread
sometime back that his engine got busted
by over boosting cause the EBC failed.

tazman

You can hook up the AVC-R to send full signal to the waste gate when there is no power to the solenoid. This way you will be limited to your waste gate spring pressure.

J Chen

Hi Tazman,
Can you also do it on a Blitz ID ?

Thanks

tazman

Sorry I don't know how the Blitz unit works.

badass951

tazman - Sorry to intrude on this thread with an off-topic post, but I just wanted to let you know that I am moving to West Chester in November. I should definitely have my new 951 then, so we will have to go out and have some fun if you are up for it. I know Reading and West Chester aren't that close, but it is a lot closer than State College is.

Dark Lightning

MBCs can fail too. It's all about rotten luck. I ran an APEXI AVC-D (yes, -D, not -R) for 3 years with never a single malfunction or issue. By far EBCs are much smoother in operation and much more consistant.

tazman

Sounds cool! I think West Chester is only about one hour from Reading. I don't remember all the details of the car you are getting done up but I remember enough to know I look forward to checking it out.