MBC without BCD?

[surfwagon]

Has anyone tried to run a MBC without using the boost cut defender? I'm asking because I'm spiking to 19 psi and settling to 15.6 psi. If I only want to boost to 17 psi will I need the Boost Cut Defender? My power mods are SRI, race pipe and 3" TMIC. Thanks

 

[07speed3]

Bump...thats a good question i was curiouse about also.

 

[Darksun280]

"If I only want to boost to 17 psi will I need the Boost Cut Defender?"

Clear cut answer is YES

you'll spike if you step on a tall gear and your boost will go above 17 psi trust me you wont like the feel of the boost cut. Get a BCD or map clamp. If you set the BC to only spike 17 you'll be holding s*** for boost through the gears

 

[surfwagon]

On my 300ZX, I set the boost to 15 psi and it stays there. The only spike I get is maybe 1/2 a psi. What's up with the MS3? We should be able to just set the boost to what we desire and not get a spike and then the gradual loss of pressure. Darksun280, I'm sure you're right. If I set it to spike to 17 psi, then I'd be boosting really low once it finally drops off and holds (before dropping off again)

 

[Bravnik]

Has anyone tried to run a MBC without using the boost cut defender? I'm asking because I'm spiking to 19 psi and settling to 15.6 psi. If I only want to boost to 17 psi will I need the Boost Cut Defender? My power mods are SRI, race pipe and 3" TMIC. Thanks

If you only boost to 17PSI you will not need a BCD. Boost Cut happens at 18PSI if you hold it for more than a couple secs.

 

[tru-boost]

yep, a quick spike wont trigger cut. if the boost hangs above 18psi it will cut. i ran my MBC @17psi for a mont before i got my map clamp. in all honesty though if you set 17 psi in the low gears you will have huge 20+psi of boost in 5th and 6th and will get cut. if you set it to 17psi in the top gears your lower gears will be the same or WORSE than stock. get a MAP clamp and set it to 20psi in the top gears. that will give you 16-18 in 3rd and 4th.

 

[surfwagon]

So what causes the MS3 to spike so bad with the stock boost controller and with a MBC? We're spiking up to 3-4 psi. If we could get a handle on this we'd be so much better off. Ideas???

 

[tru-boost]

my car did spike a bit on stock boost control. with my MBC it is minimal if at all. i run the turbosmart which uses a ball and spring AND bleeder system. the combination of those two methods allows for fast spool-up without crazy spikes.

 

[Aaron@JSC]

So what causes the MS3 to spike so bad with the stock boost controller and with a MBC? We're spiking up to 3-4 psi. If we could get a handle on this we'd be so much better off. Ideas???

an undersized wastegate most likely. If you punch the gas at a high gear you will spike up because the wastegate can't open up fast enough to bleed the exhaust away from the turbine. Porting the wastegate may solve this issue, I am still getting up the guts to port mine.

with my TBE, I spike 20 plus if I hit it. If it hangs there for more than a sec, boost cut. As of right now I am just controlling boost with the throttle..

 

[tru-boost]

i dont think the WG is undersized. usually the more boost you run the smaller the WG can be. its the cars with a 3071 and a tiny stock WG that have a problem. on a stock k04 the WG is fine. it depends on your set up. like i said i can run 20+psi and have a 1psi spike at most. it actually has more to do with the throttle conrtol on this car, not the WG.