Post here if you run WITHOUT a blow-off-valve
Jun 8, 2010, 05:51 PM
#17
Curious where this is going to lead.... or actually what is the point???
You do not NEED to run a bypass valve, many cars including down right evil track racecars do not always run valves, if you can keep spool and don't care about longevity of your turbo it will work. Keep in mind it is also a case by case bases. Boost, turbo size, TB size, mission.... etc. many things can effect how it reacts with your motor and of course driving habbits.
You do not NEED to run a bypass valve, many cars including down right evil track racecars do not always run valves, if you can keep spool and don't care about longevity of your turbo it will work. Keep in mind it is also a case by case bases. Boost, turbo size, TB size, mission.... etc. many things can effect how it reacts with your motor and of course driving habbits.
Jun 8, 2010, 06:34 PM
#18
I have had several turbo Nissan Z cars and none of them run any sort of BOV. They also run only about 7psi stock. I had one with 250K miles and the turbo was perfect. They were non intercooled as well. I had run up to 15psi on one for thousands of miles with zero issues. Compressor surge sounds cool. My other buddy bought an EVO with the BOV on backwards and it killed the turbo running 23psi in about 4 months and only about 2K miles.
Jun 12, 2010, 09:12 AM
#21
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Please correct me if I am wrong but can't the throttle butterfly flap hold 28-30psi before it is forced open?? This comes from when I had my 2000 Civic Si turbo'd and people were running boost tests and that was the number for civic a TB.
Jun 12, 2010, 01:28 PM
#22
I have gone both ways. We have a shop honda that had too stiff a spring in the Tial and had ran with basically no BOV on the street and track for 2 years before anyone noticed (755whp, 28-32psi). 67mm Precision, no damage. In fact I am thinking about buying that turbo for the GS300T I have in my possession.
We ran a stock 9.8cm turbo that way without any issues or NLTS for awhile. Very responsive for a track car. Some of this can be placement too. If you are trying to keep from venting intercooled air and keep the system "charged" move the BOV to the hotside of the intercooler on the lower intercooler pipe.
Porsche used to mount it on the compressor cover and I think the Saturns are that way now as well.
We ran a stock 9.8cm turbo that way without any issues or NLTS for awhile. Very responsive for a track car. Some of this can be placement too. If you are trying to keep from venting intercooled air and keep the system "charged" move the BOV to the hotside of the intercooler on the lower intercooler pipe.
Porsche used to mount it on the compressor cover and I think the Saturns are that way now as well.
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Tommyfacekicker (Oct 23, 2019)
Jun 12, 2010, 08:12 PM
#24
SRT4 turbos have the BOV on the compressor housing as well. I like it closer to the t-body because it is closer to the stop when the butterfly closes and doesnt let the pressure build up all the way back to the turbo.
Jun 12, 2010, 08:22 PM
#25
I think this would only matter if it was hot piped. An intercooled setup would be about the same no matter where the BOV is. Keeping it on the hotside of the intercooler keeps fresh "cold" air ready to go in instead of venting it and waiting to replace it with freshly cooled oil. Letting out hot air avoids heatsoaking the intercooler without getting gain from it and keeps the overall volume of air the motor can ingest higher until its recharged.
Jun 12, 2010, 08:43 PM
#26
Getting rid of the BOV likely won't keep the turbo spinning any faster on a throttle lift. Compressor surge will slow down the compressor substantially.
If you want to get creative, I would think something like a pre-turbo throttle hooked up with a vacuum source like a BOV could potentially improve transient response.
Might kill the turbo in a hurry too due to the negative thrust caused by the vacuum on the inlet.
You aren't going to force a throttle open since any boost pressure acting on the butterfly to open it has an equal amount of pressure on the other half trying to close it.
If you want to get creative, I would think something like a pre-turbo throttle hooked up with a vacuum source like a BOV could potentially improve transient response.
Might kill the turbo in a hurry too due to the negative thrust caused by the vacuum on the inlet.
You aren't going to force a throttle open since any boost pressure acting on the butterfly to open it has an equal amount of pressure on the other half trying to close it.
Jun 12, 2010, 08:55 PM
#28
Vacuum on the inlet should always remove the load on the turbo, thrust or otherwise. To use the extreme example to illustrate the point, consider a compressor spinning in a perfect vacuum. Can't have thrust with no air to push against. I could be wrong, but working with high vac semiconductor equipment for a living this is how my pumps work. No air, no load.
I only tried a pre-IC BOV once, on my 2g, and it sucked. There was a 1-2 second delay in it's opening. May not be an issue if that's just how long it took the air to back up to that point and open the valve, and a lighter spring may have let vac open it, but it drove me nuts. Aside from that, the main advantage I see to having the BOV at the TB is that you keep the momentum of the air column moving toward the TB, which should be a good thing...
I only tried a pre-IC BOV once, on my 2g, and it sucked. There was a 1-2 second delay in it's opening. May not be an issue if that's just how long it took the air to back up to that point and open the valve, and a lighter spring may have let vac open it, but it drove me nuts. Aside from that, the main advantage I see to having the BOV at the TB is that you keep the momentum of the air column moving toward the TB, which should be a good thing...
Jun 13, 2010, 03:58 AM
#29
The turbo Indy cars (KART) and the old F1 turbo cars all had throttles on the turbo inlet so they could close it and keep the turbo spinning. If you put the engine's only throttle on the turbo inlet, there is no need for a BOV because there would then never be a closed path after the turbo. Throttle respose then dictates no intercooler. A throttle blade before the turbo also requires a different seal setup in the turbo. The mid-80's turbo dodge cars were like this, then they switch to a blow-through throttle body.
In a blow-through throttle body, no BOV is just a bad idea. In stock trim it would have been cost-cutting.
Kevin
In a blow-through throttle body, no BOV is just a bad idea. In stock trim it would have been cost-cutting.
Kevin
Jun 13, 2010, 04:28 AM
#30
Grand National's didn't run a BOV....but that is because they are all automatics. Correct me here if I am wrong about that. Going strictly off memory. They would still surge when letting off the throttle though. Remember this strictly from dynoing one.
I don't think you'll find much solid info, especially nothing scientific, to draw solid conclusions on. Coincidental data at best. To come up with something of that sort you'd have to ask the manufacturers. Garrett mentions that it can eventually cause damage. I'd wager that with the advances in metallurgy, etc that it has become less of an issue though.
http://www.turbobygarrett.com/turbob...o_tech101.html
Oh and one more thing. When you check for thrust bearing failure on a turbo it isn't the normal side-side wiggle check. You need to check in and out play.
Email most turbo companies an tell then that you have a turbo with in and out play and didn't run a BOV. Chances are they won't warranty it.
I don't think you'll find much solid info, especially nothing scientific, to draw solid conclusions on. Coincidental data at best. To come up with something of that sort you'd have to ask the manufacturers. Garrett mentions that it can eventually cause damage. I'd wager that with the advances in metallurgy, etc that it has become less of an issue though.
http://www.turbobygarrett.com/turbob...o_tech101.html
Oh and one more thing. When you check for thrust bearing failure on a turbo it isn't the normal side-side wiggle check. You need to check in and out play.
Email most turbo companies an tell then that you have a turbo with in and out play and didn't run a BOV. Chances are they won't warranty it.
Last edited by SpoolinUp; Jun 13, 2010 at 04:31 AM.