35 vs 38 mm
 

the flanges are all the same right? so wtf is going to be the big diference on using a tial 35mm over the 38? whats the capacity of a 35?

Re: 35 vs 38 mm
 

Same flange. I don't know the difference in performance or limits, buuuuuuut I'm going to go ahead and say that you'd be okay with either or them. :y


JP

Re: 35 vs 38 mm
 

One of them has a 35mm valve. The other has a 38mm valve. Amazing, really.

Re: 35 vs 38 mm
 

you guys suck. he's only asking what the difference is. you dont have to be assholes. the difference is 3MM O0, therefore the capacity is accelerated by the momentum of the overflowing combustable exhaust fumes that carry excess molecules of get a rope.

Re: 35 vs 38 mm
 

LMAO! ;D

i know only difference between both is 0.1181099 inch :l

Re: 35 vs 38 mm
 

well since u guys are obviously retarded lol... i know size isnt ---- in comparison...

I meant about performance wise. about holding higher amounts of boost, what the limits of the 35 was, while still being reliable.

Re: 35 vs 38 mm
 

let us know what is your goal..we can let you know which one to use maybe..

Re: 35 vs 38 mm
 

::)


This guy kinda already answered your question. Either will work, and if you plan on pushing THAT much pressure the 44mm is your solution. Otherwise either will suit your standard needs.


JP

Re: 35 vs 38 mm
 

im shooting for at least 400.

Re: 35 vs 38 mm
 

What size turbo? what kind of low boost are you looking for. I'd recommend ATLEAST a 38mm.

Re: 35 vs 38 mm
 

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.

Re: 35 vs 38 mm
 

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

Re: 35 vs 38 mm
 

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.

Re: 35 vs 38 mm
 

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 :l j/k

Re: 35 vs 38 mm
 

;)

Re: 35 vs 38 mm
 

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.

Re: 35 vs 38 mm
 

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.

;)

Re: 35 vs 38 mm
 

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 ;)

Re: 35 vs 38 mm
 

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. :y


JP

Re: 35 vs 38 mm
 

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

Re: 35 vs 38 mm
 

Inertia very much has not been overcome. Look at a super peaky Honduh dyno sheet sometime... the slope of the horsepower as it comes up is a change in turbo shaft speed aka overcoming inertia. Look at a compressor map sometime if you don't believe me - at a fixed pressure ratio (wastegate settiing) the point of flow moves to the right as power comes up. On most Garrett maps you'll see each island is also labelled with a shaft speed... you cross over a bunch of those points as the point of flow moves to the right on the compressor map = change in shaft speed. Turbos operate dynamically; there is no getting away from inertia.

liveforphysics Luke was the major proponent of the big-merge-collector-fed-wastegate-tiny-turbine-stuck-off-to-the-side manifold design, and a lot of people in the industry sat up and listened to him because the kid was a boy genius with a BA in ICE at 19. Little known fact of the matter is that Luke changed his mind about the theory after actually building one and monitoring pressures, bsfc, and power output. Last I heard from him he was drillling holes into compressor covers and building custom intake tracts that were supposed to accomplish whale penis like intake ergonomics for boosted rides, and he didn't care about manifolds so long as they didn't crack.


That's false. Look at the average ---- retentive NA build vs the average turbo build that has less in the whole car than the NA build does in the suspension.

Locally, Old Man Blossfield is making 248 whp at 12 psi off a D16Z6/Disco-P in a full weight 93 Si, and running 7.70's in the 1/8th with low 1.7x 60's. Travis Grimm was making 258 whp off his 85X92mm aka 2.1 liter stroker aka $9000 longblock, laid into a gutted 93 DX, and turning 7.40-7.50's with low 1.7x 60' and some high 1.6x's. There's a 500 lb difference between the vehicles, but Old Man Blossfield runs within a quarter second of the NA hatch, and with a higher trap speed to boot. If weights were equal the NA car might sit beside him until most the way towards the 330', maybe.

There's a whole lot to be said for driver talent, too. Most turbo car owners are hooligans, and drive like it. :P

Re: 35 vs 38 mm
 

you man w/ the turbo z6 is running so quick because of proper (almost proper) turbo sizing, which is really the root of the problem in the peaky dyno honda world. like i said, with a proper WG placement you could run a smaller turbine which means fater spool and not falling out of boost between gears.

if you run a gigantic compressor you only make 600hp for 500rpm because it took your whole rev range to get the turbo efficient.

Re: 35 vs 38 mm
 

I agree with that totally, but you don't need fancy wastegate placement to get it. Look at this internally gated GT2871R dyno chart, low power is 7 psi wastegate and high power is 12 psi... what a difference in power 5 psi makes, gobs and gobs of midrange:

http://www.redpepperracing.com/galle...+11-12+psi.jpg

And the laggy drag turbos make 600 whp for a bit longer than 500 rpms... but it does have to be revved to 9200 and the driver can't lift off the gas or the car hiccoughs and falls on it's face for a split instant. Mostly due to it being an 81mm bore instead of an 84/85mm bore which would spool a lot quicker:

http://www.redpepperracing.com/galle...0-1/630+wh.jpg

Re: 35 vs 38 mm
 

its not just wastegate placement, its turbo size as well. when you can relieve exhaust manifold pressure super efficiently it lets you run a smaller turbine, which we all know creates mid-range power, with out choking the engine. it can be on a log, squarefold etc, mani design doesnt matter like you said.

its all part of a system, not just one part makes the whole build.

Re: 35 vs 38 mm
 

Disagree. There may or may not be a small trend along those lines, but for practical purposes it's worthless.

Using what you have pegged as an unideal wastegate placement, the 630 whp car above is running 0.39 bsfc... for a turbo car. Best I've heard of on a turbo Honduh is 0.38 bsfc. There is obviously nothing wrong with the system's efficiency with regard to wastegate placement and turbine sizing.

Re: 35 vs 38 mm
 

for a 630hp drag car it doesnt matter where the wastegate is because peak power is whats important. when you are trying to maintain a flat torque curve from say 3000-7500 you need a turbo that spools well and a wastegate that can decrease manifold pressure to let the engine breathe up top.


even though your intake pressure stays the same through the RPMs exhaust mani pressure continues to rise which tries makes the turbine spin faster, unless you have a wastegate to relieve mani pressure. if you keep the exhaust manifold pressure relativly constant boost will remain constant because the force turning the turbine stays the same.

Re: 35 vs 38 mm
 

The car above has a flat torque curve... As flat as the boost curve, anyway. On 19 psi wastegate its flat as a strap, everything higher just tapers but the torque curve looks just like it all the same. You can thank Brian Crower for that.

Re: 35 vs 38 mm
 

the sohc graph looks nice but on the 600hp car you could use a smaller turbine to bring boost in sooner and a larger/better placed WG to relieve excess manifold pressure once it hits full boost so that the top end remains the same. yeah it is a full drag car but most 300+hp honda dynos look similar, and since most car are driven on the street who wouldnt want mid range to go along with top end power??

Re: 35 vs 38 mm
 

Using the manifold design you espouse, a smaller turbine would create a larger average manifold pressure as the pressure-enthalpy conversion across the turbine would be less efficient.

Wastegate positioning does not take priority over turbine positioning. Even Corky Bell got that much right. Run both off a merge collector with nothing more divergent than a 35 degree divider, OMG YOU ARE SUPERIOR TO A LOG MANIFOLD.

Re: 35 vs 38 mm
 

yep. it's logical, if ur are runing with big turbo on low boost you willl need to throw out to exhaust more air then ull need a big wasgate..

Re: 35 vs 38 mm
 

i never mentioned a manifold design. i even said it doesnt matter what type of manifold. just as long as the WG and placement are correct is all that matters


a smaller turbine does make more mani pressure but if you have a WG that can release that excess pressure then you wont spike/choke the motor.

Re: 35 vs 38 mm
 

Wastegate is a important part to the puzzle. But not God of the manifold design. Please do the math on a former F1 car. 1.3 liters at 16,000 rpm and then you will know why they had small turbos with big wastegates.

Randy
PS I have a mid size turbo, with a mid size wastegate, with a mid range manifold, and guess what, it makes middle horsepower.

Re: 35 vs 38 mm
 

i find it funny that some people think what makes a wastegate work and what it does isnt true



the 3 mechanical engineers that i work with are laughing right now

Re: 35 vs 38 mm
 

Placement is design.

You are spouting Luke's feed the wastegate stick the tiny turbine off to the side manifold theory.

Placement.


A smaller turbine needs more pressure to do the same amount of work as a larger turbine. The wastegate is going to do ---- all to relieve excess pressure... all it is going to do is maintain the needed amount of exhaust pressure to acheive target intake pressure... which, for a smaller turbine setup, is a higher manifold pressure than a larger, more efficient turbine would need. That higher exhaust pressure is a loss.

If the small wastegate big turbine setups can't get rid excess turbine pressure, do you know what happens? It's called boost creep. If the system doesn't boost creep, there is no wastegate problem.


I've had to tune and resort a couple cars for local MEs, on average they do shoddy work and don't know as much as they should. Engineering is 70% theory, which means a lot of engineers are real short on real-world experience to cockslap their theories. MEs are either idiots, talented with pen and paper, or ninjas. In my experience, 1 in 100 are ninjas, the rest I could do without.

Re: 35 vs 38 mm
 

That is not correct. F1 cars use HUGE wastegates and HUGE turbos. They used to be restricted to 2 psi of boost and had to rev to 18 grand to make the target 900 or so HP. A huge turbo is needed to flow enough for 900 HP. A HUGE wastegate is needed to bypass most of the exhaust energy since very little is being used across the turbine.

They couldn't keep the motors together long enough for a good race and it was pissing off the spectators, so they were allowed 6 psi of boost. Now they only needed to rev to 12k or so to make the same 900 HP. Now the motors last for mostly the whole season.

Re: 35 vs 38 mm
 

Just about everything you said right here is incorrect.

Peak power is not important. Domestics have proven that quite nicely by showing that the first 1/8th of the track is more important for low ETs than the last 1/8th. To get down the first half quickly, you need a responsive predictable torque curve, good traction, and the right amount of wheel spin.

Next, a large wastegate is worthless on a small turbo, especially with high boost. Most of the exhaust energy is going to be going through the turbine, NOT the WG.

Exhaust manifold pressure will always rise, because of the nature of compressors. To keep a constant pressure ratio, the compressor wheel MUST, I repeat MUST spin faster and faster. Look at a compressor graph. The speed lines take a dive down.

AND that last part you mentioned doesn't make a lick of sense unless you have a constant engine speed and a constant load. That will never happen throughout the RPM range.

Re: 35 vs 38 mm
 

the 3 mechanical engineers that i work with are laughing right now

The 3 mechanical engineers that you work with are circle jerky right now, HAHAHHA
JD and I will agree 1 out of 100 are good the other 99 suck each others cocks during lunch.

Re: 35 vs 38 mm
 

Shiiit since when are mechanical engineers experts on turbo setups?

Re: 35 vs 38 mm
 

The differences between most engineers and racers is,
1.Racer will always finsh the build sooner
2. Racer will always spend less money
3. Racer will always win!!!


Randy > doens't work with any engineers, I just want to clear that up, I work with racers
PS The above post of mine was meant to be a quote.

Re: 35 vs 38 mm
 

why cant engineers be racers??

our intake manifold is on the fastest pump gas 05+ mustang (supercharged 26psi, prototype mani made 80Whp)
and we have and still are designing parts for big manufacturers

Alba racing
turner motorsports
kooks custom headers (engineers are so dumb we give advice to a company thats been around since before most of us were born)