Just a quick question about Revhard's wastegate placement. The picture of their tubular manifold below has the wastegate on only one runner. I'm still new to the game but would think that would allow for ridiculous spiking. I've already decided to go with the IP manifold but was just curious why it's placed like this.

 

well the maxrev is kinda to the one side more too , but im sure it flows very well i havent heard any complaints about it yet. . . now for this one im not sure, i have the same state of thinkinh you do though.

 

A turbos manifold system is obviously closed... create an outlet anywhere in that system and you will bleed off what you need to. I don't believe wastegate placement would really contribute to spiking.

I think incorrect exhaust piping diameters would be more prone to spiking. Or using a Deltagate altogether

 

remember that the manifold is pressurized equal too or greater than the intake side.. If your running 15psi the manifold is greater than that.. now think how the bov works.. its the same thing.. While there is flow inside the manifold its a constant pressure setup. That is why log manifolds are so effective.

 

Huh?

 

i use that same manifold for the longest time. 30lbs never spiked once with a tial

 

you're right, technically you want to have the wastegate bleeding off all of the combined exhaust gases from each cylinder pushing the turbo, personally i don't like that manifold.

 

that mani works fine

 

I think he's saying the opposite.. meaning, since "inside" the manifold before the turbine wheel you have an amount of boost being created (positive pressure)... create an outlet ANYWHERE on that system containing the positive pressure and you'll be lowering it. I personally don't believe the 1-2-3 runners in that manifold would "beat" the 4th runner to the punch in order to bleed off the excess boost... if it's closed, it's closed. Do I make sense? I just woke up...

 

well runner position placement is the ONLY solution anyone has come up with to explain why a boost spike occur.

install a 3" downpipe w/ tial wastegate and drag 3 manifold which has the wastegate placed on the 4th runner and u will get boost spike. then swap out the drag 3 mani to a revhard mani which has the wastegate on the 3rd runner and u no longer have boost spike. got any other ideas to explain this?

 

I think the DRAG manifolds wastegate is sitting on the #1 runner, not #4

 

Oh how I wish my copy of Maximum Boost will arrive soon. I'm tired of being clueless.

 

haha. yeh, i counted backwards. whoops

 

Was thinking the same thing... Lets just all get inline pros and be done with it!

 

What would be interesting is to have a DRAG manifold with the wastegate mounted on #3 as opposed to #1 to see if it solves the spike.

Simply by saying that DRAG spikes and Revhard doesn't... isn't enough evidence for me to believe it's the runner placement. But you're right, it definitely appears to be just that.

 

doesn't boost spike results from inefficent venting of the waste gas between the block and the turbo? so given that at any one time, one runner will be venting exhaust gas DOWNWARDS, and flowing straight to the turbine. Granted that there are some resistance at the turbine, but when it is spinning at high speed, resistance is much less than static. Now, in order for the gas to vent out the individual runner, it has to flow AGAINST the flow of gas, and go UPWARDS into one of the other 3 runners. Not to mention that therotically, gas will be split 3 ways ( if not 4 up aginst the original runner) into the rest of the 3 runners. So, only partial venting is done. Eventually, the gas might be vented out thru the wastegate, but since every pulse from the engine happens so fast, it might lead to boost spike, won't it?

maybe I am just oversimplifying this...

 

98Lude....you are on the right track....

There is not a constant pressure in the Exhaust manifold.....there are pulses being sent from each cylinder when the exhaust valve is open.....optimaly, the pulses could all go down a direct path through the turbo or out the exhaust.....but to regulate boost, some of that pressure from the pulses of exhaust need to be blead off from going through the turbo. If all of the pulses had a smooth routing to the wastegate there would be equal pulses to the turbo at all times, creating smoother and quicker boost build up. By having the wategat outlet on one runner, the pulses actually colide with each other when a pulse from a runner without a wastegate port goes up one with a wastegate port. This causes all kinds of tubulance and disrupts the flow of air into the turbo causing uneven pulses (or none at all) which can slow the turbo. But this can also cause spiking when a pulse from cylinder without a wastegate port can not make it up the runner to the wastegate port, causing it to all go through the turbo, which makes it spin faster and increase the boost.

 

First off, someone mentioned maximum boost. Awesome book, definitely worth the purchase price. I must have read mine 5 times at least...so interesting.

The last person who reponded has the right idea. Obviously the wastegate needs to divert the exhaust pulses away from the turbo to regulate boost creation. The wastegate outlet should be optimally placed (and these are the two reasons I don't like that manifold)

-it should be able to gather and purge exhaust gas from all cylinders. I.E. you want to place your outlet at the main point at which all exhaust gas meet and enter the turbo.
-it should not be at a sharp angle much like the manifold pictured is, it should be a smooth angle...gas doesn't like taking sharp *** turns

you want the gas to be able to flow out of the manifold easily. When the wastegate opens up you want the exhaust gases out asap cuz you've already reached your boost goal. A 90 degree bend isn't going to facilitate efficient exhaust gas removal.

 

My thoughts exactly. Does the book cover this topic?

 

that manifold doesnt spike becuase even tho it is on only one runner, it is very close to the collector. As a result the pressure differentials are diminished by the presence of the wastegates "runner".

Also one thing to consider is that this runner is 1.5" The hole on the drag manifolds which spike is more like 1 inch and is very small.

As far as controlling "boost creation" goes, you should consider it more controlling turbine speed, or shaft speed to get more accurate.

 

I was at a loss for words...I'm posting on this board and working my butt off at the same time hehe

 

Yes it covers it, quite nicely in fact...trust me man order the book, it's great

 

no problem, i knew you had the concept down pat, just wanted to let others know

 

I have that same manifold and have never had any problems with boost spiking. Sometimes I see a very small amount of boost creep but its within 1-1.5 psi. It seems to do the job quite well..

 

Did it two weeks ago...still waiting.