Toyota MR2 Message Board - View Single Post

Loki · 07-02-2006, 08:18 PM

Just to be up front: for me, the stock BOV is an ugly turd.

Every BOV works on a pressure differential with a spring and diaphragm with one side on the charge pipes, and one side connected to somewhere behind the throttle body; only the HKS and the stocker appear to operat solely from the manifold side with check valves to create the necessary pressure differential (internal on the HKS). I'm not sure why so many people in the community favor this method of creating a pressure differential to open the valve as you have to pull against pressurized air to open the vavle with that system as opposed to most others where the pressurized charge air is pushing the valve open. If you are stock ecu equipped, certainly the stock BOV rerouted or an aftermarket BOV re-routed is most likely to run the best due to the metered air issue, but also keep in mind that the average stock BOV has well over 100k miles and 10+ years of use -- rubber and plastic don't last forever (seals, hoses, and VTV may well crack or leak).

I ran a Greddy Type R on my stock ECU and it was fine. I would shoot flames on occasion when shifting due to the slight rich condition when the BOV blew off. I'm not sure that's flaw as I quite enjoyed it (www.koracing.net/img/LokiFlames2.jpg). Proper adjustment of an aftermarket BOV is certainly critical. You want to balance the ease of it blowing off (i.e. get the best response so it will very quickly blow off when the throttle closes) to protect your turbo from surge, with it hanging open too much and causing un-metered air to get in, or too much of it getting out and the car wants to die. My usual adjustment method was to be able to hear it blow off at idle by manually manipulating the throttle (very low load on the engine).

For ease of use, the Tial is probably the best. It's one of the largest BOV's available at 50mm diameter (for those going to bigger turbos) and there is no adjustment on the BOV. I installed one last week on a stock ecu equipped car an the car took a day or so to *relearn* to catch itself and keep the engine idling when shifting into neutral, but after that it has been a champ. I experienced the same thing with the Greddy BOV when I had the stock ecu also.

What I also am not sure of is the capacity for the stock one to hold boost and not leak or blow apart at very high levels. I run 25psi at the track and know that the Tial is good for much more (40+psi). I've heard of stock ones failing above 18 - 20psi -- but granted, they are all old.

Which would you rather see:

This:

or This:

07-02-2006, 08:18 PM	#49 (permalink)
Loki KO Racing Dude Join Date: Jun 2006 Location: Hillsboro, OR Posts: 104 Thanks: 3 Thanked 1 Time in 1 Post My Google Map iTrader Rating: (3/100% )	Just to be up front: for me, the stock BOV is an ugly turd. Every BOV works on a pressure differential with a spring and diaphragm with one side on the charge pipes, and one side connected to somewhere behind the throttle body; only the HKS and the stocker appear to operat solely from the manifold side with check valves to create the necessary pressure differential (internal on the HKS). I'm not sure why so many people in the community favor this method of creating a pressure differential to open the valve as you have to pull against pressurized air to open the vavle with that system as opposed to most others where the pressurized charge air is pushing the valve open. If you are stock ecu equipped, certainly the stock BOV rerouted or an aftermarket BOV re-routed is most likely to run the best due to the metered air issue, but also keep in mind that the average stock BOV has well over 100k miles and 10+ years of use -- rubber and plastic don't last forever (seals, hoses, and VTV may well crack or leak). I ran a Greddy Type R on my stock ECU and it was fine. I would shoot flames on occasion when shifting due to the slight rich condition when the BOV blew off. I'm not sure that's flaw as I quite enjoyed it (www.koracing.net/img/LokiFlames2.jpg). Proper adjustment of an aftermarket BOV is certainly critical. You want to balance the ease of it blowing off (i.e. get the best response so it will very quickly blow off when the throttle closes) to protect your turbo from surge, with it hanging open too much and causing un-metered air to get in, or too much of it getting out and the car wants to die. My usual adjustment method was to be able to hear it blow off at idle by manually manipulating the throttle (very low load on the engine). For ease of use, the Tial is probably the best. It's one of the largest BOV's available at 50mm diameter (for those going to bigger turbos) and there is no adjustment on the BOV. I installed one last week on a stock ecu equipped car an the car took a day or so to relearn to catch itself and keep the engine idling when shifting into neutral, but after that it has been a champ. I experienced the same thing with the Greddy BOV when I had the stock ecu also. What I also am not sure of is the capacity for the stock one to hold boost and not leak or blow apart at very high levels. I run 25psi at the track and know that the Tial is good for much more (40+psi). I've heard of stock ones failing above 18 - 20psi -- but granted, they are all old. Which would you rather see: This: or This: