I do think it is very possible you could have some kind of small air leak. 
Finally got the FMIC on and the car got slower!
Finally got the FMIC on and the car got slower! My front mount is finally done! I ended up using the Vortech Mondo bypass valve. Unfortunetly, my boost droped about 2 lbs. and the car runs 2mph slower ( according to G-tech and seat of the pants ) in the quarter. Anyone else experienced this? Also, where can I get a smaller 8-rib blower pulley? I have the 3.4 ATI right now and was told thats the smallest they make. I currently see about 8 psi of boost.
Launching!
Joined: Oct 2004
Posts: 296
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From: Oregon
Originally Posted by BOOSTAT4500
My front mount is finally done! I ended up using the Vortech Mondo bypass valve. Unfortunetly, my boost droped about 2 lbs. and the car runs 2mph slower ( according to G-tech and seat of the pants ) in the quarter. Anyone else experienced this? Also, where can I get a smaller 8-rib blower pulley? I have the 3.4 ATI right now and was told thats the smallest they make. I currently see about 8 psi of boost.
Wow thats a lot of boost to loose to a IC swap. Are you sure you don't have a leak, or slipping belt. You have the SDCE set up right, tension that sucker a lil more. Seat o' the pants really has to be calibrated, and 2mph on a g-tech can be due to weather different launch...etc...
IC's that ive seen have a .2 to .5psi drop @ 15psi with a good bar and plate set up.
IC's that ive seen have a .2 to .5psi drop @ 15psi with a good bar and plate set up.
I'm pretty sure there's no leak. There isn't any adjustment on the bypass that could cause this, is there? I've got the tensioner about as tight as it will go, but I'll double check it anyway. Watching the boost gauge it seems to climb steady. The .2 to .5psi drop that your talking about is from the blower outlet to the manifold right? I don't know what my drop there is, I'm just comparing my boost level to when I had the stock IC's.
boost drop also comes from greater density of air(cooler air) after the ic, if your ic has good efficiency, your iat's will drop ALOT and your boost as well because the air is less dense and you are actually better off. and the only real way to test is on a true dyno or at the track. gtech is nice for giving a guestimate but it cant simulate all the real world circumstances of a track.
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iTrader: (2)
Joined: Nov 2002
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From: Taking back some video tapes
How big is the intercooler. I'll almost guarantee it's the pressure drop across the intercooler that's causing the "loss" of boost. You may have too small of an intercooler.
They do make smaller pulleys in 8 rib.... I had a Richard racing 3.3" blower pulley i sent with my kit when i sold it to osuhunter. he might still have it. It was from Richard racing and i believe they make a 3.2" also. When i switched i also saw a 1-2 psi increase over the stock twins. They were a ristriction on my setup.
Kyle
Kyle
Originally Posted by Blackbird
i dont how it's possible for you to lose boost over the twins.
check for leaks. J picked up 2psi when he made the switch right J?
what brand of fmic is it?
check for leaks. J picked up 2psi when he made the switch right J?
what brand of fmic is it?
So more boost added more HP/TQ which equated to faster trap speeds and 1/4mi times.
Something isn't right, I'd check everything over. I can't see loosing power unless you had the pipe routing neck down excessively or too long. Going to a larger core over the anemic ATI twins should always be a step in the right direction HP/TQ and boost wise.
Originally Posted by frcefed98
Not only did I go from 13psi to 15+ with the FMIC change over, I was trapping 123-124mph consistently with 125 being my all time best. MAF and injectors also maxed out earlier too. The car would only manage 117-8mph with the twins on the same tires.
So more boost added more HP/TQ which equated to faster trap speeds and 1/4mi times.
Something isn't right, I'd check everything over. I can't see loosing power unless you had the pipe routing neck down excessively or too long. Going to a larger core over the anemic ATI twins should always be a step in the right direction HP/TQ and boost wise.
So more boost added more HP/TQ which equated to faster trap speeds and 1/4mi times.
Something isn't right, I'd check everything over. I can't see loosing power unless you had the pipe routing neck down excessively or too long. Going to a larger core over the anemic ATI twins should always be a step in the right direction HP/TQ and boost wise.
I agree with you Jer......... Check every connection to be sure.... it could be a small thing....
Kyle
The intercooler is the same size as the OBX one. I don't base everything on the G-tech runs, it was just for reference. I'll hopefully be going back to the track soon to find out for sure. Hopefully it is an air leak or something. As I understand it though, a bigger space with the same amount of air in it will have less pressure, not more.
Also think of it this way, cooler air is more dense. Its like putting a balloon in the fridge, it gets smaller. Same amount of air, just more dense and takes up less space.
all of this is good provided that your charger stop making pressure, but since the charger is always making boost a drop in pressure is a leak.
I changed my 6 lbs pulley to a 9 lbs pulley and could only make 5 psi, all I did was change the pulleys but I lost pressure, after going over everything I found out that the spring in the bypass valve could not take the extra boost and it was leaking, after removing the bypass valve i did a test run and BAM 10 psi on a 9 lbs pulley at 6000 rpm's.
I changed my 6 lbs pulley to a 9 lbs pulley and could only make 5 psi, all I did was change the pulleys but I lost pressure, after going over everything I found out that the spring in the bypass valve could not take the extra boost and it was leaking, after removing the bypass valve i did a test run and BAM 10 psi on a 9 lbs pulley at 6000 rpm's.
On The Tree
Joined: Aug 2003
Posts: 151
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ok guys, think about it. adding an intercooler is adding a restriction to the plumbing if you do NOTHING ELSE to the system. the same amount of air is being pushed by the blower, however you are trying to force it through an intercooler now as well as the plumbing that was already there.
so the intercooler cools down the charge (which reduces the "boost" pressure) - you have to then RETUNE the system to take advantage of the lower IATs. add timing, and maybe lean it out a little bit. You will make up for the loss in power and then start seeing gains.
Simply adding an intercooler could easily cause a power loss if you do not retune. An intercooler does not allow any additional mass of air to enter into the system, it just cools things down and while doing so adds a restriction. Tune to take advantage of the cooler IATs!
so the intercooler cools down the charge (which reduces the "boost" pressure) - you have to then RETUNE the system to take advantage of the lower IATs. add timing, and maybe lean it out a little bit. You will make up for the loss in power and then start seeing gains.
Simply adding an intercooler could easily cause a power loss if you do not retune. An intercooler does not allow any additional mass of air to enter into the system, it just cools things down and while doing so adds a restriction. Tune to take advantage of the cooler IATs!
I would make sure my line is plumbed directly into the intake pass side, with large tubing all the way down. And if its adjustable, tighten the spring down some. With mine the race ready, i had to go all the way flush with the lock nut. And make sure nothing is on the belt and pullies. And like someone else said check your tension if its only at stock on the tensioner. With mine the stock tubing and where i had it plumbed was not adequate, and stock adjustment was way way off....Spring pressure and boost hold it shut and you are running a small pully. With leaks i think the bov is the most common thing missed. And retune it afterwards. 
Launching!
Joined: Oct 2004
Posts: 296
Likes: 0
From: Oregon
It is pressure drop from the IC. But even then, you shouldn't feel hp loss unless your afr's are different. Lets put it this way.... Lets say you have 20psi before the IC. When that 20psi goes through the IC, the air gets colder and turns into 18psi. The colder the air, the more dense it is (reason for the pressure drop). That doesn't change the amount of oxygen going to the engine though. I hope I didn't lose anyone
So, even though you have that change in pressure, all that oxygen should still be the same, just in a smaller package (pressure drop). The only way you would lose hp is if either the MAP or MAF sensor doesn't compensate or over compensates for correct afr. Tuning could be off. The only way to really know is on a dyno like some people have mentioned. That way you can see correct hp readings w/ afr instead of going by mph
So, even though you have that change in pressure, all that oxygen should still be the same, just in a smaller package (pressure drop). The only way you would lose hp is if either the MAP or MAF sensor doesn't compensate or over compensates for correct afr. Tuning could be off. The only way to really know is on a dyno like some people have mentioned. That way you can see correct hp readings w/ afr instead of going by mph