Wastegate Creep vs Wastegate Plenum

[Jesse OBrien]

Since I'm relatively new to turbo technology, I've been doing a lot of research and an excessive amount of parts ordering. I'd really like to be as sure as I can be that I'm doing this right, so forgive me if this is a little irrelevant/silly/inconsequential.

 

Anyway, the article that spurred the thought process can be found here:

http://autospeed.com/A_111119/cms/article.html

 

Essentially, it suggests using a plenum and a bit more hose running to the wastegate reference inlet (from the compressor side of the turbo). This keeps the wastegate completely closed longer, and theoretically allows a more direct buildup of boost while low in RPMs. As pressure increases, the wastegate receives correct reference and opens appropriately (in theory), keeping peak pressure within safe levels.

 

My concerns are that I'll get a pressure spike just after reaching peak boost rather than having the wastegate open at the correct pressure. I believe I'll be running 8psi (.5bar) until I've sorted out my ECU/suspension/chassis/etc, then safely increase my boost pressure. I could also see compressor surge being an issue, since there is a delay in the wastegate's reaction time.

 

Ideally, this will simply allow me to get to that 8psi more quickly and keep me in a safe range. I just want to know if the idea is unsafe/unsound.

 

In that same vein, I also thought the intercooler would make a very nice (convenient) plenum, and if the theory behind this practice is sound, I could reference the wastegate actuator off the intake ductwork just before the throttle plate. As I said, the delay concerns me, but I'm curious as to whether anybody has experience with a setup like this. Thanks in advance!

 

(oh right, this is on an l28et, which means the reference from before the throttle plate is very convenient)

[GrayZee]

I can tell you how to get boost VERY fast, but the problem would be keeping it below 8psi. A checkball style manual boost controller will make the boost HAMMER on! My experience is that it does not really matter if you set it 10 or 20psi it's ability to increase boost response is the same, but even at it's lowest setting it will increase boost slightly. My advise is to run it stock until you get your ecu/chassis issues sorted out and get a cheap manual boost controller like this: http://www.geocities.com/chmwatson/FAQs/mbc.html

 

You can get those on ebay for like $10

[streeteg]

Youre best bet is an electronic boost controller for control over boost. It uses an actuator that allows the gate to open at an exact pressure, and maintain it with limited variance. They are more expensive but allow you to run options such as boost by gear and scramble boost. They work in conjunction with your ECU and do very well for the money.

 

-E

[Jesse OBrien]

Thanks for the input guys. GrayZee, I don't have the option to run at stock (or even stock-ish) boost since I don't have the stock turbo, and am automatically forced to go with an external wastegate.

 

The electronic boost controller would definitely work, but you're right about them being expensive. It's more than I care to afford at the moment, so for the time being I'm going to experiment a little with the boost plenum idea and a passenger to gather data. I may be able to automatically log pressure and o2 sensor output, so I'm going to do a little experimentation with plugging them into a sata plug and logging the output. Wish me luck.

[streeteg]

The easiest/cheapest way to control boost is to run no boost controller and just let it operate off spring pressure. With the properly combined springs you can acheive a static boost level for the cost of the springs

[GrayZee]

The easiest/cheapest way to control boost is to run no boost controller and just let it operate off spring pressure. With the properly combined springs you can acheive a static boost level for the cost of the springs

 

 

This is true, however you will not get the boost to come on nearly as fast as you would with some sort of boost controller.

 

You can run stockish boost with a external gate as long as you use the right spring but if the turbo is alot larger than stock you might get boost creep higher up in the rpm range, if it is quite a large turbo you might wanna look at something bigger than a 38mm wastegate. As big turbo's and low boost dont exactly work that well together.

 

Electronic boost controllers are great, no doubt about that, but it's all about how much money you want to spend. The primitave manual style controllers do work quite well especially when they cost only a tiny percentage of a good electronic one.

[Jesse OBrien]

This is true, however you will not get the boost to come on nearly as fast as you would with some sort of boost controller.

 

You can run stockish boost with a external gate as long as you use the right spring but if the turbo is alot larger than stock you might get boost creep higher up in the rpm range, if it is quite a large turbo you might wanna look at something bigger than a 38mm wastegate. As big turbo's and low boost dont exactly work that well together.

 

Electronic boost controllers are great, no doubt about that, but it's all about how much money you want to spend. The primitave manual style controllers do work quite well especially when they cost only a tiny percentage of a good electronic one.

 

I have a 60mm wastegate sitting around for when I'm ready to up the boost to that level. It's not a MASSIVE turbo, but the compressor side is a fair amount larger than stock.