Where oh where is my boost going?

[Alter Ego Trip]

When I first installed my Vortech, it came with a 3.60 pulley. With that pulley on, max boost I could make was 8lbs due to elevation. During remote tuning, it was recommended by the tuner to drop a couple pulley sizes to get back to 10lbs. I went to a 3.33 and during datalogging I would just see it clip 10 every now and then.

My tune was finalized a couple weeks ago and I took it to the dyno to see the differences. On the rollers I could only get 6lbs of boost. Since then I've run it through the gears a few different times with similar results. In fact, I don't see 6-7lbs till well into 3rd gear, first and second seem to hover around 5.

The weather is almost identical to what it was when I was datalogging. The only thing I've changed on the motor has been a high flow catted X, which I know wouldn't change by 3lbs. I've checked all the connections, and they are tight and leak free as far as I can tell. The only thing left I can think of is the belt, but I can't imagine that being an issue. I didn't put on a smaller belt when going with the smaller pulley, but it didn't appear I needed to. The tensioner is right in the middle of the range, and I don't detect squeeling, black powder on the pulley, or freying. I can't imaging it slipping at only 10lbs of boost.

Any thoughts?

 

[j-stang]

still using the plastic bypass valve?

 

[Alter Ego Trip]

still using the plastic bypass valve?

Yes sir.

 

[bigray327]

That's probably your problem. Those stock Bosche valves suck! I would replace them with something better, like a mini race valve.

 

[Alter Ego Trip]

That's probably your problem. Those stock Bosche valves suck! I would replace them with something better, like a mini race valve.

Hmmm. I would look into picking one up but I really want to convert over to a blow through which is a bit of money at the moment. I think it would be counterproductive to go this route and then have to upgrade a couple months down the road???

Thanks for the help via PM.

 

[KrisR]

Both my Bosch valves have been fine since the install last spring (around 13k miles ago). I see 15lbs on occasion. Not saying for sure that yours isn't leaking, but I would suspect something else first, like a boost leak. I would doubt it's belt slip also, as I have a 2.87 6-rib pulley without any problems (granted this is with a Steeda tensioner, but I had a 2.95 with my stock tensioner and had no slip, but the tensioner broke at the track).

Can you describe in more detail what's happening with the boost? If you do a low-rpm to the top 3rd-gear pull, does the boost continually increase or does it level off or fall off at higher rpm?

 

[Alter Ego Trip]

Kris,

Here's the scenario.

After 3.33 pulley install I would see 10lbs during WOT, with fairly steady boost climb. During shifts (auto), it would drop to 8-9. This was a couple weeks ago. On the dyno the car made 6lbs boost.

Recently. During WOT through the top of 3rd gear; instantly it jumps to 5lbs boost, then holds there till right about 6200-6500 where it jumps up to about 7. During shifts it drops to about 5. It doesn't really seem to climb with any linear motion.

I am going to replace the plastic tubing with some rubber hose just to rule out a gauge issue. The car really doesn't seem to pull as hard now though as it did a couple weeks ago (maybe in my head).

Both my Bosch valves have been fine since the install last spring (around 13k miles ago). I see 15lbs on occasion. Not saying for sure that yours isn't leaking, but I would suspect something else first, like a boost leak. I would doubt it's belt slip also, as I have a 2.87 6-rib pulley without any problems (granted this is with a Steeda tensioner, but I had a 2.95 with my stock tensioner and had no slip, but the tensioner broke at the track).

Can you describe in more detail what's happening with the boost? If you do a low-rpm to the top 3rd-gear pull, does the boost continually increase or does it level off or fall off at higher rpm?

 

[Alter Ego Trip]

I just want to thank everyone for their input. I decided to look into the bypass valve, and change out all of my vacuum hoses just for good measure. After disassembling most everything, I grabbed the bypass and put some vacuum to it. The valve closed as intended. After checking out all of my vacuum lines for leaks and coming up empty I decided to try pressurizing the vacuum line of the bypass. I hooked the compressor to it on low output and low and behold, the canister had a hairline crack at the bottom that was spewing air of of it. I epoxied the hole up (until I get the replacement in), and took the car out for a spin.

11psi later with a steady climb, and 555r's spinning through second I am once again like a cow in tall grass.........




























Utterly Tickled. Thanks again guys.

 

[mrmonk7663]

Glad to hear you got it working. FYI on the blow through setup. You can convert to blow through fairly cheap. If you have an intercooler already, then that means you have 2 bypass valves (or should) You would simply unhook the big tubings and you can run the plastic valves open. So that part is free (good to upgrade when you can though) The only thing that you will really need is a MAF, flange, and access to a welder. HPX makes a meter that even in a tiny 3" pipe will go to 650hp with NO mafia. You can pick them up between $207-$250 NEW depending on where you do your shopping. I just did this conversion. Total cost for the meter, flange, and having a local guy tig weld it was $260. And I no longer have big ass in the way bypass routing tubes Hope this helps.

 

[KrisR]

Cool, glad you got it figured out.

 

[NastyStang113]

Nice!! How is the tune now that the car is running tops?

 

[Big50]

Nice!! How is the tune now that the car is running tops?

I'm wondering that myself, since it sounds like the tune was written while not making the kind of boost he is now. If so might want to get it re-tuned.

 

[Alter Ego Trip]

Nice!! How is the tune now that the car is running tops?

I must say I am very happy with how it is running at this point. It will roll my big 305 555r's through 2nd. My original tune netted 370 hp with 3.31 gears and 18" tires at 8lbs boost on a Mustang dyno. Same dyno after Justin's tune netted 412 on equal/less boost w/ 4.10 gears and 20" wheels. The WOT shifts are a million times better now too.

My only complaint with the current tune is my auto shiftpoints at mid throttle. Justin just emailed me back a new tune to try and remedy that so we'll see how it goes.

Big 50. The car was building boost as expected when datalogging. This just happened within the last couple weeks. It might have been doing it earlier to a lesser extent, but it was unnoticable at that point. You can definitely feel the difference now, compared to a few days ago.