Tom-Guy

No, actually, large gates are for low boost on big turbos. Small gates work just fine at 16+ psi.

Some of the low backpressure GT40+ need dual 44 or larger gates to maintain 12 psi... dual 44's actually pulled 12 creeping to 14-15 on the GT42R'd EP3 I tuned back in the spring.

samson

Hmmm, interesting. Thanks for the quick tip. I assumed as a majority of builds that run through here either would suffice. I see, once again, assumption leads me astray and answers are found in JD.


JP

Tom-Guy

Most of the good tech gets handed to me these days, sadly. I need to get back on track with the coil dwell stuff for eCtune... I have about two weeks between semesters to ---- off and do stuff like that.

HiProfile

I don't know why thats so hard to understand though. A turbo's exhaust system is basicly a matter of pressure, and essentially everything will create a pressure drop to some extent. The less pressure drop you get from the turbine, the less of a pressure drop the wastegate must be (flow better). Have a more restrictive exhaust w/non-recirc dump, and the WG size needed is smaller, and vice-versa.

Its like a long checklist of +'s and -'s, and when you get a negative, you get creep. :1

BTW idk bout anyone else, but it scares me that JD is HMT's 'go-to' guy j/k

Tom-Guy

Racintweek

manifold design should lean towards wastegate placement before turbo placement, it will allow you to run a smaller turbine and not choke off high rpm power because it can efficiently relieve manifold pressure when you hit full boost.

Tom-Guy

How do you efficiently convert exhaust stream energy to boost when the exhaust stream is fighting for a smaller amount of area across the turbine wheel, 'tweek?

Most manifold theory is junk science, IMO. Bottom line is boost works. Biggest change is spool is from pairing runners, biggest change in efficiency is from merge collectors and smooth transitions on both turbine and wastegate entries, give me a log manifold and I'll make more power than you can lay to the ground.

Racintweek

once the turbine is spinning inertia has been over come so keeping it going requires a lot less pressure, if you have an escape for the uneeded pressure then creep and choking wont occur.

you are right most of the theories that people have about manifolds are useless, equal length doesnt mean as much as people think, flow is useless. most designs dont really make more power over the next just shifing spool/powerband. when you are drag racing WG placement isnt that big of an issue but for a daily driven or track car the difference in drivability/spool time is spectacular and you can creat a much smoother TQ curve (should it really even be called a curve?? )



p.s. there is a reason a 250hp N/A car will smoke a 250hp turbo any day of the week, why wouldnt you want the response of an N/A car w/ the top end of a turbo car. old school F1 engineering taught us this a while ago

samson

Little lost here.....

I saw dyno proof of a log making around 30whp LESS than the ramhorn manifold soooooooo what does this say about spool time, WG placement, and overall power?

EDIT: 4th row, 1st vid (Full-Race Test...)
http://www.panekmechanik.com/video_main.html Love thier vids.


JP

Racintweek

the loss of power in that vid is the fact that the turbo is sucking in exhaust when it hits full boost due to no dump tube