Old vs. New
 

I have one of the older FMII kits on my '95, and I'm in the process of changing the exhaust setup. I just got the divorced gases downpipe from BEGi, and I'm staying internally gated for simplicity's sake, and because I'm not striving to go higher with the boost for now, or for a long time for that matter.
I was looking at my manifold, I don't have a picture of it, but to describe it as simply as possible, all of the runners are completely even with each other, the outlet-to-turbo flange is between cylinder 2 and 3, and about 2-3 inches above the runners. As far as I know, it's definitely one of the older designs.
Anyway, I was looking at the new cast manifold that BEGi has, with the directed pulse design, and I also found one of their older units that looks the exact same, but is without the directed pulse design. It's still brand new and for sale by a private seller.
Would there be any benefit to moving to either of those units (and I'm assuming that the directed pulse design is superior to the manifold without it)? Or should I stick with what I have and be happy since I'm not trying to make all the power in the world.
Thanks in advance.

i think all the directed pulse is is a barrier that turns the gases into the turbo, instead of running into each other causing a bunch of chaos :robert:
markp knows more about it then i do, well hell anybody does i just keep hearing markp preaching on something about it :nuts:

Haha!
I kinda figured that's what it was, hoping it was a self-explanatory name.
And another thing I've been wondering since I've never had this happen on any other car I've boosted, is say I'm in 5th gear doing 70 mph, and I go full throttle, it will sound like the air is "chugging" in the intake for a few seconds, and then as RPMs go up, it smooths out into solid boost. If I'm doing the same speed and downshift to a lower gear, solid boost immediately. The car is running somewhat rich in boost, so I don't know if it's because of that or if it's the manifold design and the way the gases are moving and being pushed through it. Maybe someone can clear that up too.

maybe its the turbo wheels gaining speed? they can't just simply start spinning at however many thousand rpms. but i'm just speculating, someone else will chime in with more info

I could not imagine there being any real world difference, certainly no difference to be worth the extra cost and effort involved.
Convert over to the "new style" intercooler setup if you've got money to burn.

I'm not sure, just because the wheel is always spinning in proportion to engine speed. I'm thinking the gases are not being smoothly delivered into the turbine at lower RPMs and this is where I'm getting that disturbance, because it almost feels like small pulses. Hopefully someone has a definite idea or similar experience.
Like I said, it's never happened on any other boosted vehicle I've had, from RX7s to a turbo Saturn.

I was hoping you'd chime in.
Not really money to burn, just looking at worthwhile upgrades, and wondering if this is one of them while I have everything taken off to get ceramic coated.
IC setup comes later and will be DIY since I don't really consider the kit prices to be wallet friendly.

Actually, it's not. The speed at which the turbine wheel spins is related to engine load. Let's say you're casually cruising along at 3,000 RPM. In this condition, the load is very small. The throttle plate is not open very far, so the intake manifold is under vacuum and not much air is being consumed by the engine. The amount of gas being exhausted out of the engine is small and thus the amount of energy acting upon the tubine wheel will be minimal. It will be turning, but not very fast.

When you step on the pedal, suddenly the VE of the engine increases, and as more air is going into the cylinders, more exhaust gas is coming out, providing more energy to turn the turbine, causing it to speed up independant of the speed of the engine.

If the speed of the turbine were always proportional to the speed of the engine, then it would be trying to produce boost all the time and we'd need byass valves similar to those commonly used on positive-displacement superchargers.

Sorry, that is what I had meant to say. I actually have no idea why I said speed. Guess it just made sense in my head at the moment, long day at work.
Anyway, need more input on the manifolds and the other issue.

Gotcha.

Seems that the question of the manifold is ultimately one that only you can answer. Is the current design of the Bell manifold superior to the old one in terms of flow and performance? Yes, it probably is. Is the difference between the two signifigant enough to justify spending $400 on a new one? Not if it was my money.

If the manifold is cracked or otherwise damaged, then I could see replacing it. But if it's not damaged then I would honestly go with it. The power gain you're going to realize through a decent intercooler and a proper tune will far outweigh whatever tiny gain the newer manifold might provide.

If it was cracked I would be calling bell anyway. Didn't they have like an uber warranty on their manifolds?

If the turbo will be in your hands, and if you want to spend a couple hundred to improve performance, consider having the compressor outlet ported, the turbine inlet and outlet ported, maybe if you're froggy have, the inside of the turbine housing extrude honed (gets rid of casting imperfections). That should give you a good increase in spool and a nice bump up top. I think that would be a better application of probably the same amount of money (considering that you would recoup some costs of the new stuff by selling off the old). Also, talk with BEGi about ceramic coating the exhaust mani. Steph was saying that it doesn't have any significant thermal advantage, and they do it for cosmetics.

OK, so on the differences, keep what I have. And it's in perfect shape, not a problem with it.

Ben, I may consider the porting and honing. Sounds like a better investment. Just have to find someone worth a damn to do it properly. And the ceramic coating was more for cosmetics in my case as well. The manifold and turbine housing are very ugly at this point. IDK, I just like everything to look good. Personal preference.

Any ideas from anyone in the case of the "chugging" issue? To add to it some, it only happens when I give it 100% throttle. Anything less than 75% throttle, it doesn't seem to happen.

Personally, I think old iron manifolds look cool.
The "issue" sounds tune related. Accel enrichments perhaps. But that's a WAG.

You could make a plate that slid in that accomplished this.

I don't know of any back to back testing to show that the directed pulse design is better, but logic suggests that it should be better. Would I spend $300 on it if I had a good manifold already... probably not.

The directed pulse design was my idea, and I would like to think that the reason it was implemented was because it did work better.

Mark

see i knew he would chime in :bigtu:

Alright! Thanks for the input. It's exactly what I wanted/needed to know.
And I'll see if the "issue" exists after I get the car retuned.