Hi All, I'm new on this forum and I badly need your help. The problem is in low boost, on 32kompressor. I'm running a 60mm supercharger pulley and dual CAI and getting only 15.3-15.5psi of boost.

I used to see high 17s 17.8-9 on 62mm, then I noticed that the boost was low, I took off the pulley and saw the bearing in pulley was weakened and I changed the whole pulley with new bearing, the new pulley is 60mm and I cant still get the proper boost.

what I checked: I checked up for leaks in system, and there is no single leak, I changed 3 map sensors, as I read the boost from obd2, I thought the sensor might had gone wrong, but still boost is low, and acceleration is low too. I checked the clutch behind pulley, cleaned it and it looks like everything's ok. I have no belt slipping issue, as I'm using belt wrap. I used to measure 100-200km/h times on racelogic, I had about 9 sec, now I'm getting 10.XX. the only thing I'm now able to think, is that possible that something has gone wrong with supercharger rotors, that causes the low boost.

If anyone has had the similar issue, or U have any ideas, I'll be grateful to hear from you.

p.s. another small question, my supercharger is making about 16000rpm, at 6200 engine rpm, on 155/60mm pulleys, what must be normal boost at about 400 meters above the sea.

 

I found out answer on my first question, it turned out that the belt was overtensioned, and the car wasn't able to make boost on high rpms. But the second question is still actual, what boost do you get with such mods, I've read guys makin about 20 psi, at about 16000rpm of their charger, I'm not still able to step over 17.5

 

I'm close to sea level and mine will reach 19 peak psi with just a 178 crank pulley. It sounds like you have some belt slip to me even though you don't think so.

Les

 

belt slippage, will make boost fall down at peak rpms, mine is building boost all the time at WOT, just seems low to me even 17.5 psi

 

Or slight intake manifold leak or leaks towards peak boost; even if he doesn't think so. OP; Have you had your intake manifolds off before, and how did you test your charged intake tract?

 

Check your filters in dcai they might be full of crap, that's what happened to me, was down on boost, cleaned the filters after almost 2 years and boost is back up

 

I have found that low boost is due to frictional loss in a clogged ( airpath ) intercooler. Mine was gross when I changed it and new intercooler increased the REPORTED BOOST. Intercooler is between SC and intake manifold - clogging will restrict boost .....WW

BTW my intake being cross connected reduces the peak boost by 3-4 # as I am flowing more air into the motor, what with both runners from the super charger feeding both intakes and the cross connected manifolds. Ill look for the photo to explain it better. WW

 

Here is my intake showing the cross connected intakes, sharing the passages from the output of the IC. MUCH GREATER AIRFLOW INTO ENGINE WHICH LOWERS THE STANDING PRESSURE, BLOWER IS MOVING MORE AIR AND NOT STACKING IT UP TO AS HIGH A PRESSURE. The DCAI I put together has bubble wrap insulation to "drop" or NOT pick up heat from the engine bay.

My hood is opened ( NEGATIVE HOOD SCOOP ) up to allow much more airflow reducing under hood temps, but the hood still is way over 170 degrees on a normal day. Something to consider. Enjoy Woody

 

thank you guys for your ideas

filters are ok, I cleaned my intercooler that is under SC 3-4 months ago, I dont think it would get such clogged for such a short time. besides the cooler no leaks. yes I've taken off my manifolds for several times, but I tested them carefully when putting on and when searching for leaks. I'll test them again these days with another method and I'll post if I find any leaks.
waldig \
what is your sc rpm and what boost are you making?

 

Iam reading 17, newer gauge showed 19. Blocking off the crossover passages made 20 or so. Stock pulley and 178 pulley. Woody

 

I dynoed my car on friday, on Dyno dynamics. I've 354whp max. afr is about 12.2 in peak rpm, boost 17.5, timing -22. I guess the numers are normal for that boost

 

Nice numbers

 

Thanks morphh

what sparks are you people using on high boost? I've stock ifr6d10 from ngk, thinking getting new ones, shall I get bkr7-s?

 

I must be a little dumb on this matter, can you explain how the SC moves more air at a lower pressure.

 

its my understanding that the airflow is restricted due to the stock wye after the stock intercooler and the fact that a single cylinderbank gets air only from a single source after the wye. when crossconnecting the intake manifolds you probabely get 30-50 procent more airflow because the cylinderbank gets air from both sources. so running the air through both sources means removing a restriction which results in a pressure drop.

sorry that my english isn`t better

I like the idea of a crossover intake pipe. We all know exhaust crossovers balancing V8/V6 engines exhaust pulses. The intake side may benfit from a crossover as well: a blower is nothing else than an air pump and pumps out the air in pulses. Seems to work on woody`s engine (2 psi pressure drop).

i will try to crossconnect the stock intakes on my slk32 and get rid of the stock wye section. i am pretty sure a single 50 mm crossover pipe will work fine for me. Aiming for cooler air as well btw

Steven

Berlin Germany

 

today in 20 c I tested the car again boost was normal I think, it hit 18.9 in fourth gear, 18.4 in 3rd. I guess I'll get over 19 at 5-10 degree