Do mods effect max psi boost.. I been doing more reading and with a 15% pulley shouldn't I be making 15lb of boost I,am only seeing a max of 11psi. My mods are :15% pulley, light crank , header , no cat and pacesetter exhaust ,jcw injectors , forge intercooler , intake and those are my only mods I can think of that would effect my max boost . The car is a rocket and runs great. My gauge could be inaccurate too but if I'm sapose to be at 15psi I need to replace my gauge and if I'm still at 11lb of max boost I need to start looking into other things , like possibly my Alta couplers not sealing fully and I guess after I get a little input and my new gauge in a few days I will chime in again with the results of the new gauge
and IF around 11psi is normal on my setup what size pulley should I run to be at around 15-17psi max.

 

Could be as simple as the Forge intercooler robbing you off of some boost.

 

And is that because of the increase in size ?

 

Yeah, without getting super nerdy with chemistry, Boyles law says that the pressure of a given mass of an ideal gas is inversely proportional to its volume at a constant temperature, so if you increase the volume of the system after the super charger, the pressure is going to decrease.

I guess I got nerdy anyway, but at least I didn't go into temperature differences....


How are you measuring boost? via OBD? or did you plumb a boost gauge? I'd tend to think that if the car runs ok, then it's probably fine. You could always swap the OEM intercooler back in and see what you get for readings.

 

First, doing a 15% pulley and nothing else, in most cases will give you approx 13 ish psi with no leaks.
There are so many variables that could give you a 2-3 psi drop, including a simple combination of small things.
The only way to know for sure is to do a smoke test and/or start swapping parts one at a time, to see if there are any changes.
You'll want to look at the I/C boots, vacuum lines, even that the BPV butterfly closes tightly, it all can matter.

 

I have a vacuum boost gauge installed ,by me following threads I've read instructions .
I didn't think a smoke test would have worked as I can't add boost and I don't have a vacuum leak fir sure but it could be blowing past a bad seal under full boost, all though I get it to stand on that 11psi if I hammer it in a high gear where if it waaaaas leaking wouldn't I see boost drop offs ?
I would try swapping out the intercooler but I don't have the stock one anymore ..
sorry I'm bombarding you guys...I just want this car sorted out perfect as I plan on doing some racing in it come summer and if I'm going to run it hard I want it done correct..
Do they make an intercooler diverter to fit into these forge intercooler or am I forced to just install weather strips on it so it seals to the hood and helps force air through it not over it

 

As I've noted, MOST aftermarket coolers do not have the flow directors / straighteners that the OEM/GP intercoolers have.
Smooth airflow has a large influence on pressure outcome.
Buy only radiators that have flow straighteners for the most pressure to the combustion chambers.

Mike

 

For what it's worth I have a 15% pulley, M7 intake, JCW catback, and stock intercooler. I see around 13-14 psi (Haven't even gone close to red line in this car). It makes sense that a larger intercooler would reduce your boost levels.

 

Full pull send it!!

 

Lol rite ? How could you mod your car but yet never do a WOT pull and make sure you don't have issues with it..just me though..lol I do a mod, I hit the closest longest freeway onramp by me and make sure everything is all good..if my car can't be beat on Abit and handle it, I don't want it ..because there's going to come a time some cocky old man or young kid thinks his all stock all factory bought not built 50,000$ car is all that ,then my 2500$ monster Cooper eats it .

 

lol my supercharger cost more than your entire car

 

Lol I know I know. I’m just a bit hesitant on a 140k mile motor with factory injectors, fuel pump, and tune. If I had the 380cc or 550cc injectors I’d be a bit more confident in not leaning it out at redline WOT. I would just hate to have it lean out and end up needing to rebuild the head; especially on a daily driver.

 

Nothing wrong with 6500 boys!!!

 

Mine has 200k miles . 15% pulley , jcw injectors , intake , exhaust with no cat and wrapped headers , light weight crank , bigger intercooler , coilpack wires and ngk plugs and possibly an lsd...I run my car hard . I go wot to the redline atleast once every other day....in the 8months of owning the car all I've had to replace were the front tires.. I do run 91octane and cut my tank with 3gallons of e85 to boost the octane rating to around 95 according to the charts..car is and has been running absolutely amazing..let's hope it stays that way 🤞
This is actually the most dependable least maintenance car I've ever owned .

 

Awesome! I'll have to eventually look into some bigger injectors but I'll want a tune after that. So then may as well put a header on it before getting the tune... It snowballs quickly!

 

Lol sure does..
Jcw injectors don't need a tune, the ECU can adjust accordingly for them. Mine never threw a code or anything and ssssshhhhhh I bought the eBay knock offs for 40$ brand new. Exact copy of jcw's I did soooooo much reading before I bought them and when I installed them was ever so careful testing everything out. It's been 4 months and not an issue..no tune or anything but I did have all the other mods 1st..only cel I have on is for rear 02 sensor because of no cat but I'm looking into mil eliminators for the R53. I know they make them for other cars and I've used them and passed emissions doing so,lol..

 

Are these the same 380cc injectors that require the splicing in of a connector adapter? I was curious about the spray pattern of those...

 

No. Here are the ones...but I see the price has gone up though now
https://www.ebay.com/itm/4PCS-NEW-38...0AAOSw3CdcfUcH