TIAL or Dejontool mod? Which will hold 25PSI & NOT surge?

[sweet97]

This is driving me crazy!! I am using a Holset HX-35/40 and need to boost to 25psi. I have the motor and mods EXCEPT for an acceptable BOV. Tried one and it either would not hold 25psi or with a heavier spring would cause massive compressor surge! I am considering the TIAL but have done a search and it seems guys are having the same problem, surge. Accordeing to the TIAL website I should use A 7# SPRING WITH MY CAMS. Would a 7# spring hold to 25=PSI? At $30. per spring I can't afford to not get it right the first time.
How about the Dejon leak stop mod/Dodge garage mod. Both seem to be the same with the dejon mod a bit more sophisticated. HELP! I need to boost to 25+ psi and NOT surge at lower boost/part throttle conditions, relaesing the throttle!? Thanks, Mark

 

[Steve93Talon]

We've had good luck with the Dejon mod. It holds 30psi to redline consistently. We're currently not even running the little device that comes with it, just have the lower hole plugged and the side vented. The only difference is low-boost driving, barely notiveable though. Just tap the bottom hole and thread in a set screw, and drill a hole in the side of the passage.

 

[shleppy]

I'm bringing this thread back instead of starting a new thread since I'm having the same problem. With the 1g bov with the dejon tool leakstop mod I can hold 30psi with no problem, but I'm getting terrible compressor surge at all the wrong times. Anything part throttle in third gear and up will surge terribly starting around 5psi, which shouldn't cause compressor surge. On the highway in fifth I can barely even step on the gas without surging and I refuse to believe that at 3400rpms and 5 psi I'm outflowing what the motor can injest. Relevant mods are slowboy gt3076r surge ported, gm mas, 1g bov vented to atmosphere, stage 4 ported slowboy heads with 264 cams, smim and slowboy 2g race frontmount. Is anyone else having this problem, and is there another bov that will solve this problem?

 

[MyBeatGSX]

The BOV you're running has zero effect on WOT surge.

 

[andymoraitis]

The BOV you're running has zero effect on WOT surge.

But it certainly does on part throttle.

 

[shleppy]

yep, were only talking about part throttle, low boost surge here. It's a pain having to always shift as soon as I start making boost, or always downshifting so I'm over 4000 rpms.

 

[MyBeatGSX]

But it certainly does on part throttle.

In what way? Say he's accelerating steady at like 30% throttle and 5psi, and it goes into surge... which is basically the situation if I read that correctly... what effect does the BOV have on that? Shouldn't it just be sitting there closed and minding its own business?

I thought this kind of surge is caused by the engine not flowing enough/the turbo flowing too much, this is why they have anti surge ported compressor covers... which he's running . How does the BOV fit into that?

 

[andymoraitis]

On a BOV like mine which is heavily crushed, if I roll into the boost in fifth and generate 5psi and then snap off the throttle, I have no problems. If I ask the BOV to release very small amounts by backing off the throttle just enough to stop boosting, it'll surge. It's the BOV not releasing fast enough because it's crushed to hold a ton of boost.

Sounds like it's time to call FP and see what they say, however I still think it has something to do with the BOV. What we need to establish is whether this is happening when he's lightly getting off the gas or if it's happening on acceleration only.

 

[shleppy]

light acceleration, only part throttle, and also letting off the gas a little.

 

[Maglin]

Yep I was having the same issue. The problem with the Stock 1G BOV is that it's not adjustable. If you wanted to spend the time and effort you could cut the top off and drill a hole in the top cover and install a softer spring with the use of a set screw w/ guide pin and flat washer that fit's said guide pin. Then ensure the screw isn't leaking any vac/boost and you now have a smaller version of the Greddy Type S. That is with the lower chamber vented mod.

Personally that is to much work. The inlet of the 1G BOV is really pretty small. If you are running a medium frame or large frame turbo past 25+ PSI then it won't let enough air out and cause surge. I just let it surge on my holset. I would drive around it but their are some things out of your control and the occasional surge happens. Now I have a Greddy Type S. With the HX35 and the BOV adjusted properly I have no surge. But if I want to run over 30 PSI low boost surge is just something you can not get around. The one thing everyone loved about my old 1G BOV was when it did blow off it was sooo loud and long. Sounded very wicked. Not like a sneeze most BOV's make.

Also the reason for low boost/part throttle surge on cars running 30+ PSI is from the heavy setting on the BOV requried to not leak at those boost levels. It's just to hard for the BOV to work at lower boost settings. And surge is created.

So the best bet is to get an adjustable BOV. With a compressor and a gauge on your UICP pressurize the system to 3-4PSI above your set boost limit. Ensure that is what is in the pipe with the gauge. Then back out the BOV adjusting screw until it starts to leak. Now tighten it up and stop right at the point where the valve stops leaking.

That is the best you are going to get. If you still get low boost/part throttle surge then try setting it right at your boost target. If you still have issues you are faced with a decision. Lower your boost and thus also your BOV spring pressure. Try using 2 smaller BOV's. Try a Tial (They are premo once they are set up right). Or live with the surge you have. If you have anti surge ports on your compressor cover tinny bits of surge won't kill your turbo. I'm not saying it's good for it. But it will let the air go around the outside of the blades instead of right up through the inducer.

Aside for those Idea's I wouldn't know what else to do. Most people running large frame turbo's mainly only drive their cars on the track. The low boost/part throttle surge isn't an issue. And BTW a standard Garrett 50trim is by no means anything close to a large frame turbo. Large frame turbo's flow around 65+ lbs/min @ 25 PSI. Just so you understand what I'm refering to as large frame turbos.

 

[sweet97]

I had that 5psi surge VERY badly. TIAL with 7psi spring was the fix. Tial and 9psi spring still caused some probelems. Get the Tial and then be sure to try a 7# spring if the 9# is not helping eenough. mark
I have some extra time and wanted to say the surge I had was so violent is shook the entire car! Especially at 5psi with a stiff spring in a Forge BOV. Just letting off the throttle a little would be enough to cause this to happen. A stiff spring is not required to keep the BOV closed under high boost wth a well designed BOV. It turned out to be the opposite as the weakest spring available for the TIAL, the 7# spring is what made my car drivable again. I was running an HX 35/40 Holset. Mark

 

[shleppy]

Thanks for all the suggestions and replies. I'll probably just end up trying out a tial and play around with that to see how much surge I can tune out with springs. It's good to know that I'm not the only one who's faced this problem.