rufretic

iTrader: (37)

I've been working out some bugs on my set-up. Changed the converter that we think was slipping & robbing power. The other thing I had to workout was lowering the boost so my 80lb injectors won't be over 100% dc. It was making 25psi with an open inlet and it was recommended by my tuner to bring it down to around 20psi. Changing the pulley is the typical way to lower the boost but I'm limited with options because I have the super pulley on the head unit which only comes in one size and I have a custom machined cog on the crank. No one sells a cog pulley for the crank so in order to change it I would have to do another custom one and that gets expensive.
I've decided to try to lower the boost by restricting the inlet instead. This way I don't need to spend a bunch more on a new pulley and it's easy enough to bring the boost back up when I have more fuel and stronger heads. I've restricted the inlet by adding a double screen, 4" 90 elbow and a 4" air filter. The inlet to the blower is 4.5" so I'm hoping by bringing it down to 4" and adding the restrictions in airflow, I should loose at least 3-5psi. If I loose more than that, I can always remove one or both screens to get it where I want it.
Now assuming I get the boost where I want it, is this going to cause any additional stress on the blower? I've heard of people using restrictor plates on the inlet to reduce boost so I'm not the first to limit the inlet but I just want to make sure it's not going to cause problems. I know bleeding off the boost is not recommended by procharger because the blower needs the pressure as the rpms go up or something like that, I know it's not good, otherwise I would have tried the wastegate thing. However, I havn't heard any negatives of just restricting the inlet. Please help me out if you know anything about this as this is all new to me and I'd hate to hurt the head unit. TIA.

AFASTYZFR1

iTrader: (55)

Can't you just get bigger injectors or add meth and leave boost where it is?

Brent@LPE

Increased IAT,s by restricting the inlet.

Brent

ak95ta

iTrader: (3)

Isn't you bypass valve adjustable? Loosen it up a little bit where it might bleed off some air. Did you not think a F2 might give you this sort of problem, haha? I had a similar problem with my YSi, it puts out 24#boost. I just went with 95# injectors.

Mr.Big

I have not had this issue, and much data logging has been done... ZERO difference was detected in IAT's...
restrict it and be happy!!!

rufretic

iTrader: (37)

80s are the biggest unless I convert to low imp which I don't want to. Meth is an option but I don't like the added risk of a malfunction or running out and blowing my block.
Also, with either of those options I'd be making too much power to feel comfortable with stock 317s. Once I upgrade to 6 bolt heads, I'll bring the boost back up and upgrade the fuel system.

Increased compared to what? I don't see how they could go higher than what they are with 25psi. I do understand it would make sense that they would be the same at 20psi restricted as 25psi non restricted because the blower is spinning the same. They would be increased compared to 20psi non restricted because the blower will be spinning faster at 20psi restricted. My iat s wont increase, they'll just be the same as they are at 25psi, do I understand this correctly?

Bleeding off boost is bad for the blower, so I've read.
I knew the F2 would make a lot of boost but my build isn't finished, the stock heads and inadequate fuel system are limiting what I can do right now. I just want to be able to enjoy the car for the next year while I save up for the heads.

I hope it works the same for me, good to know thanks.

onfire

iTrader: (17)

Biggest concern I would have is sucking a screen into the supercharger. Make sure those babies are properly anchored as they are going to have some major pressure against them. ECS might have some advice for you since they use an inlet restriction on some of their set-ups....I truly undestand where you're coming from on cost/complexity, but I'd pulley down.

rufretic

iTrader: (37)

The pulley would be my choice too buuuut, not only is it cost, it's a lot of down time, it's a pain! No body makes them. I have to find the right size cog pulley then once I get that in the mail, I have to send out to a machine shop and make sure they get the exact bolt spacing, which I'm not even sure how to do that. The pulley I have on it now was done by the guy that machined my block, I gave him my crank and had him make a perfect ballanced fit. Just seems like a lot of work to go though for a temp pulley.

Frost

iTrader: (45)

+1
.......

AFASTYZFR1

iTrader: (55)

why not just spin the motor a little less

LS1 SPEED

iTrader: (22)

I say with a 3.5" tube, filter and less RPM you should be o.k.

I prefer trying this if you are not going the pulley route over the screens.

rufretic

iTrader: (37)

Thanks for the input Larry. Lower rpms should be fine because it's just for the street for now, I'm not chancing it at the track until I put better heads on, then we can up the boost and figure out the fuel. Won't be till next year though, for now I just want to have some fun on the street.

The car should be a lot better this next time I bring it in. I quieted it down quite a bit. Still 3" true duals but now I have a Borla off each header and then into a dynomax x pipe muffler. It's 10 times quieter, all straight thru still but I'm sure it's more restricted than no mufflers. I can't wait to drive it with this Chance converter I got a deal on. I talked to Marty and it sounds like it should be super tight. I'll take it for a test drive tomorrow, just got to drop it off the jack stands. I'll be calling you soon so Jim can do a quick check on the tune before I hit it on the streets too hard.

engineermike

When you restrict the inlet, the hp required to drive the blower doesn't decrease. So, you're getting all the parasitic losses but less boost out of it. It reduces the efficiency of the FI system, which was already lower than turbo setups.

kp

iTrader: (34)

Thats right, you are losing a fair amount of power by restricting the inlet as opposed to reducing the blower rpm, especially with that big of a blower.

Slowing it down (while keeping it somewhat in its efficiency range) is the best way to do it. Obviously restricting the inlet is not the best way of doing it, but it is the cheapest and most practical for you.

rufretic

iTrader: (37)

That makes sense. I would never try to do this with a finished set-up or for max power potential obviously. I just need something temporary so I can enjoy driving the car around, I just don't want to damage anything in the process and with the injectors at 114%, I consider that dangerous. Lower boost is the easiest/cheapest way to keep it safe so I can play with it a little while I save. The car has already been down for over two years and I just can't wait another year. Once I can afford some $3000 heads and an upgraded fuel system, it will go back to a non restricted set-up and that's when I'll be going for max potential on the set-up and as much boost as it will go with this pulley combination. It sucks having limited funds because I can't do everything the right way but if I won't be doing any damage, I can live with making a couple hundred less rwhp for the time being.

BigRich954RR

iTrader: (1)

PUT the filter on and see how much boost you lose with just that.

What pis are you running the 80 at ?

LS1 SPEED

iTrader: (22)

look forward to seeing the car soon

427

iTrader: (3)

If you restrict the blower inlet the power to drive the unit will go down as will the top boost. The positive side is your area under the curve will be better with the restricter than if you pulley down. The other thing that sometimes would happen if using a restrictor is air noise going in the restriction.

Kurt

barnat

iTrader: (59)

I would pull the pully and take it to a machine shop and have one made 1/4 to 1/2 bigger which will slow your blower speed thus reducing your PSI .I have custom pullys made all the time for my scavanging pump kit that i made up for the INCON TT and now the APS TT.You'de be shocked what the machinest can do with a piece of round stock aluminium .LOL You can probably contact a blower company or yours to ask them (EXACTLY) what size pully you would need for your 20 PSI goal .I probably would stay away from the restriction idea because of the added heat that will go with doing that .Have a pully made and be done with it!LOL Good luck man

'Trust'

iTrader: (24)

If you are set on restricting boost I'm an advocate of making the blower work a little less hard. Restricting the inlet will put more strain on the blower while still spinning at a faster RPM, I'd just swap pulleys.