93 2.4l DOHC Shadow

[Shadow]

That's what I thought too back in the day but it makes sense, a log manifold is like a 1/4 pipe, my example, so your slamming the pulses thru twists, turns, and its getting slammed into walls, turns, turning back on itself but due to all the gas's sharing the same area, its forced thru increasing velocity but also with more restriction. A header allows the gas's to flow more freely so at lower rpm, they don't have as much velocity and now act like they are going thru a 3" pipe, but at higher rpm's, they are not being held back anymore by the manifold and the other cylinders, now the turbine and housing etc are the restriction. I could be off base though.

I wouldn't say the log Ever has more velocity than a header, like you said, the gasses are bouncing around like a pinball machine, so Loosing velocity. I would say it has more Volume faster to work on the turbine wheel.

Also, I think it's been proven by now that the log mani is Not the restriction ppl thought it was. If the system isn't otherwise restricted up stream of the mani, the turbine wheel/housing + anything after it will ALWAYS be the restriction! (up to 500WHP anyways)

[turbovanman²]

I wouldn't say the log Ever has more velocity than a header, like you said, the gasses are bouncing around like a pinball machine, so Loosing velocity. I would say it has more Volume faster to work on the turbine wheel.

Also, I think it's been proven by now that the log mani is Not the restriction ppl thought it was. If the system isn't otherwise restricted up stream of the mani, the turbine wheel/housing + anything after it will ALWAYS be the restriction! (up to 500WHP anyways)

I would say it has velocity as the gas's are so close to together, all empty into one log and virtually no runners hence they are trying to get out faster, whereas a tube header, they have more time to get to their destination, at low rpm's. Again, I could be wrong.

[Reaper1]

Where have you seen somebody report slower spool time with a properly executed header vs. a log manifold!? I, personally, have NEVER seen that report!

The velocity inside the manifold/header will be a function of cross-sectional area, pressure differential, temperature, and CFM. The LOCAL velocities inside will be affected by the design, but your exit velocity going into the turbine housing will just be basically dependent on those 4 things. Once the mass flow has gotten to that point, the header/manfold have NO effect on the efficiency of the turbine system. It is up to the turbine housing and turbine inducer to make the most of what is delivered to it.

The internal volume of the log manifold may be able to overcome its flow design flaws up to the point where there is enough pressure differential to drive the system. This in turn can help the engine breathe and is probably the key to the ported stock manifold doing as well as it has. However, a correctly designed header SYSTEM WILL outperform a log manifold EVERY time in EVERY aspect.

I agree with some others' assessment, there is something else causing the performance plateau.

[turbovanman²]

Lots have reported later spool switching from a log to a header. Even Aaron dynoed a 2.2 back to back and his experienced later spool with the header.

[BadAssPerformance]

Lots have reported later spool switching from a log to a header. Even Aaron dynoed a 2.2 back to back and his experienced later spool with the header.

Is it just "later spool" or is is "moving the power band upward in the RPM range" ?

For example, going from stock cast manifolds on a Magnum V8 to shorty headers you will lose low end grunt but gain high end HP... and no spool is involved

[turbovanman²]

Is it just "later spool" or is is "moving the power band upward in the RPM range" ?

For example, going from stock cast manifolds on a Magnum V8 to shorty headers you will lose low end grunt but gain high end HP... and no spool is involved

Both, from what I've read. I can't comment on my header as the A/R changed giving me a false back to back,

[Austrian Dodge]

Lots have reported later spool switching from a log to a header. Even Aaron dynoed a 2.2 back to back and his experienced later spool with the header.

i think it was moving the powerband to the right, but i couldn't find the thread.

[turboshad]

I'm still trying to learn about the exhaust side of the turbo as there isn't a whole lot of information out there on it. I did come across this which is a good read but still doesn't answer all my questions.

http://www.tercelreference.com/tercel_info/turbo_exhaust_theory/turbo_exhaust_theory.html

As for spool time sure I want it to be as quick as possible but I'm more concerned with top end power. Almost everything on the engine is favoring higher RPM performance and the turbo needs to do the same. I'm currently shifting between 7800-8000 and would like to move that up further into the 8200-8500 range as I feel the cams are still wanting to go there. So if I don't get full spool until 5000RPM I'm not too concerned as I am well above that for most of the 1/4. From what I can find higher RPM needs a larger A/R so maybe this is why it is choking up. As for the back pressure I would expect my exhaust PR to be worse than Rob's since I am making the same power with way less boost. I'm going to speculate that his back pressure will be higher but my ratio will be worse since we are pumping relatively the same mass flow of air but his pressure is higher. An equal length header should help spool time since it's job is to maintain the exhaust velocity. I won't go and say my header is anywhere near ideal. I picked a generic 1.5" weld el and made it equal length with a not so great collector. I don't think it is total crap but it could definitely be better with more thought and what I have learned since I made it. If I switch turbos a new header will be made as I would also go external gate. I'm not sure what I'm trying to say here so maybe I'm just spilling out my thoughts on the subject. I'm curious to see the exhaust PR as well so I hope I get a chance to do that this season.

[turbovanman²]

DJ, quit beating yourself up on that header, its not pretty but obviously it works, still a great job,

i think it was moving the powerband to the right, but i couldn't find the thread.

You mean this one-

http://www.turbo-mopar.com/forums/sh...tubular-header

Dyno chart-

http://www.turbo-mopar.com/forums/sh...l=1#post416418

There is also a Honda thread on the intrawebs, a built turbo engine and they used a log manifold then switched to an equal length, IIRC, the log made more power down low but fell down on top, the equal was the other way around.

Here is the Honda test, yep, the log spooled the turbo earlier but choked up top.

http://www.full-race.com/articles/Bs...st_writeup.pdf

Reaper, the manifolds I believe your talking about are the HX35 threads, where the Ford guys put a regular one on, then make a true TS and drop spool by 1000 or so rpm.

[Reaper1]

I just looked back at Aaron's thread as well as the Honda thread. Because Aaron was having issues with his clutch, the graphs were hard to read, and there was no boost pressure vs. engine rpm to look at. By his own admission it was not tuned correctly either, so to me this means that part of the system wasn't optimal. It was a GREAT test and it gave a LOT of insight, but for this discussion's purpose I don't think it really helps.

The Honda write-up did note a later spool, BUT, looking at the graphs it couldn't have been THAT much later as the difference was almost nill, and then the header took off and smoked the log manifold.

So, for all technical intents and purposes, yes, it seems that turbo headers *can* produce a slightly later spool, but the difference is so small, and the gains in the powerband are so great, that I think if there is a significant difference there needs to be a change to the system made somewhere.

[Shadow]

So if I don't get full spool until 5000RPM I'm not too concerned as I am well above that for most of the 1/4.

So is 5000rpm where you hit full spool? Just curious.

From what I can find higher RPM needs a larger A/R so maybe this is why it is choking up.

Agreed, this is what I've always believed to be true which is why I was never worried about running a .48 A/R on a 2.5. I never bought into the "it's a 2.5 so it need the .63 to breath" statement that everyone was making. After all, it's a lower RPM mtr.

In my mind the 2.2 was the mtr that needed it more because of the higher RPM it turns.

[BadAssPerformance]

Agreed, this is what I've always believed to be true which is why I was never worried about running a .48 A/R on a 2.5. I never bought into the "it's a 2.5 so it need the .63 to breath" statement that everyone was making. After all, it's a lower RPM mtr.

In my mind the 2.2 was the mtr that needed it more because of the higher RPM it turns.

A 2.2L moves the same amount of air at ~6500 rpm as a 2.5L does at ~5750 tho right?

[Shadow]

A 2.2L moves the same amount of air at ~6500 rpm as a 2.5L does at ~5750 tho right?

I'm guessing that would greatly depend on the 2.2 and the 2.5 that were being compared. Put it this way, drop an F4 cam (properly) into a 2.2 and with No other change the 2.2 is going to out -breath the 2.5 hands down. So the difference in flow between the two mtrs is Less than a cam swap. A .48 A/R housing can breath 300-350 WHP when done properly.

There was a time (maybe ppl are still doing this) when the "thing to do" was swap a .63 A/R turbine housing on a stock 2.5 with stock turbo. This is the example I was refering to. We did the opposite 10 years ago or so on a 300hp Daytona and the car went Faster than any comparable build that I could find.

So, this is Not to say that Any 2.5 wouldn't gain from a larger A/R housing, just use some common sense. If your mtr is operating at a low RPM (under 6000) then the HP your making will more than likely determine what size A/R you should be running. Once you start raising your PB you Should be able to tell wether you need a larger A/R by how well the turbo holds boost up top.

IF DJ's A/R on his current turbo is too small, I would expect him to be dropping out of boost at higher rpm as the turbo will be going into "Choke" and overspinning in the higher power range.

What will be interesting to see with these turbos is what's going to happen first. Can the BP raise so fast that the turbo doesn't even get the chance to "choke"? That wouldn't make too much sense to me?

I'm running at a low RPM (7400 limiter) and have kept it there for this exact reason, I Want to see how far this turbo will go. I Don't want to run it out of RPM and I currently have enough RPM and gear with the slick size I'm running to be able to trap 150MPH in 4th gear.

So this is what I've been watching; how much more duty do I need to run at higher rpm to keep the turbo in boost. That, and how much drive preasure I'm running. So far, so good!

[turboshad]

Boost is definitely not falling off and full boost is in the low 4000 range last time I checked. On my 1/4 mile passes the boost was creeping up a touch in 4th so I have no doubt it can make more pressure. I'll try to get some screen shots of the log later. I'll see if I can find a street spool response one too but it's been a while since I've done that.

I picked up some parts yesterday for the exhaust tap. Since I don't really pay any attention to the EGT I'll just take that out and use the 1/8NPT hole already there. Additionally I am going to run a line from the pressure side of the turbo so I can switch to that signal for a pass and record the pressure drop across the intercooler and all the plumbing. I'm excited to see the results. I got the word that as long as my wife isn't in the hospital she doesn't care if I race. I love that woman.

[turbovanman²]

Don't you love woman like that,

As for your spool, hmmmmm, interesting as the TIII guys say they get full spool around 3200 rpm.

Also can't wait to see what you find.

[turboshad]

a) I have pretty aggressive cams which will delay spoolb) I have yet to see many low RPM spool claims backed by a log. Perception and reality are often two very different things.

[turbovanman²]

a) I have pretty aggressive cams which will delay spoolb) I have yet to see many low RPM spool claims backed by a log. Perception and reality are often two very different things.

LOL, I agree but many seem to chime in the same. I am happy with mine but just wish it was easier to build boost off the line, lol. Still trying to find a .63 housing for cheap,

[Shadow]

Boost is definitely not falling off and full boost is in the low 4000 range last time I checked. On my 1/4 mile passes the boost was creeping up a touch in 4th so I have no doubt it can make more pressure. I'll try to get some screen shots of the log later. I'll see if I can find a street spool response one too but it's been a while since I've done that.

I picked up some parts yesterday for the exhaust tap. Since I don't really pay any attention to the EGT I'll just take that out and use the 1/8NPT hole already there. Additionally I am going to run a line from the pressure side of the turbo so I can switch to that signal for a pass and record the pressure drop across the intercooler and all the plumbing. I'm excited to see the results. I got the word that as long as my wife isn't in the hospital she doesn't care if I race. I love that woman.

Reminds me of my own wife, she actually gets excited to go racing with me!

Don't you love woman like that,

As for your spool, hmmmmm, interesting as the TIII guys say they get full spool around 3200 rpm.

Also can't wait to see what you find.

Who Claims HE351 full spool 4th gear at 3200rpm? I have yet to find anyone in our community that spools faster than my 8v. (not trying to be a smart a$$ here either, I Really want to know/see, cause it should be possible.)

[turbovanman²]

Reminds me of my own wife, she actually gets excited to go racing with me!



Who Claims HE351 full spool 4th gear at 3200rpm? I have yet to find anyone in our community that spools faster than my 8v. (not trying to be a smart a$$ here either, I Really want to know/see, cause it should be possible.)

Jackson, and a few others-

http://www.turbo-mopar.com/forums/sh...l=1#post839716

[turboshad]

I'm still willing to bet if they logged it thy would fine their spool is allot later than what they thought. So until I see some sort of proof. I know I have one in 3rd before the head work with neon cams I will try to find. It is for sure later with the Crane 18s.