rmerchant3

Mine was at 4 to start with. Lowered it all the way to 3200 to see if it helped, but it surges before VTEC and through VTEC up until about 6500-7000rpms. VTEC does seem to help smooth it out, but it may just be the increasing RPM's as well. How much would you say yours is surging?

I just installed the 3.2 pulley and it is still there. Seems like the smallest I can go is 3.4

CTRLFRK

I'm bad I know bumping this thread from the dead but what ended up happening? Is this still a random thing? About to send my 1220sl off to superchargerrebuilds.com in Texas to have it converted to a 1200sl, wanting to run a 3.4 with 5.45 crank. What would I be looking at hp and tq? any surge issues with a 3200 vtec on an ap2 and also is my walboro 255lph enough pump with my id1050x flashpro setup?

SuperEJ25

When you guys are surging, what does it sound like? I have a Vortech V3 Si on a smaller motor also. My SC gearing is probably not relevant to your since it's a different motor/car , but I run 7" and 3.33" pullies. If I floor it at ~5300rpm it works fine. If I floor it at low rpm it sounds like ignition cut, almost sounds like launch control. The boost goes updown up down and it sounds like garbage machine gun dundundundundundund or bangbangbangbangbang until I let off of the throttle. I know that I am operating near the surge line but really could use some advice on what it sounds like on the car?

Interestingly, 5300rpm on my car is 40,000 impeller speed, which is 35 #/hour surge line. I would NOT say I am flowing that much air....

SuperEJ25

Here is a video of my problem.

Problem is at :47 I start you off at :37

F1TwoThousand

Finally someone who posts audio and video of a problem. Sounds like some kind of ignition cut. What fail safes are you running?

s2000Junky

Typically both spark blow out and belt slip IF they are an issue, happen near peak trq first, and that's going to be up high in the rpm range on centrifugal blower set up and a 4 cylinder, not down low ...and then no problem up high. I'm more apt to think the engine is detonating which can be prone to happen at lower rpm where the engine is under more strain/load generally. Detonation could be caused a few different ways, either starving for fuel in that rpm range or too much timing advance there or both are the typical tune aspects that would cause this. But the youtube sound quality for me isn't that good so its hard to really pinpoint the finites of the sound, but this is just my general thoughts on it and some food for thought. I never had compressor surge on throttle before so I cant say what that would sound like. I don't fully understand how that quite works either so I couldn't offer anything on the possibly of that happening at low rpm vs high. As far as centrifugal blowers on an F20/22 platform, I do have a lot of experience at the full range of boost levels with 3 different blowers and have never experienced it. I think its generally not a thing unless there is something whacky/out of the typical going on.

SuperEJ25

The ecu only has fuel cut, no ignition cut fail safes. That is why it is particularly odd.

Timing reduced to 12 degrees had no impact. ECU registers no knock.

Plugs gapped at 0.20" down from 0.28" had no impact. Car drives great above 5200rpm at WOT, up to 18psi @ 6700rpm (I haven't ventured above there yet) with fat 11:1 AFR including water meth injection, so to me that really points away from ignition problem.

I know I am "on the edge" of the surge line, with this rather large Vortech V3 Si which is equivalent to the OP's Novi 1200. The biggest changes since it started that I can think of are colder weather + better pulley setup (same gearing, but bigger pullies better tensioner and another rib) which is why it made me think of compressor surge.

SuperEJ25

Alright I am back. I induced a boost leak with the BPV and it "works" fine. No bucking or surging but obviously it is losing boost on the high end. I'm going to try a bigger pulley but I am 99% sure this is/was compressor surge. My little 4 banger cannot flow enough at low RPM for a big v8 supercharger.

I know a lot of folks have never heard of this happening, but what I think happened is when I switched to a better belt and pulley setup (less belt slip), combined with COLD DENSE air , it pushed me over the edge of the compressor surge line at low rpm .

s2000Junky

I had a little myself, but I wasn't concerned with it. There is a difference between undersized evac/off throttle fluttering and on throttle Compressor surge. I think you might be conflating the two. The only thing you really risk by an undersized blow off/evac, is potential blown oil seals in the blower - Maybe if severe enough. What your talking about and in vid is ON throttle, so there is no BOV fluttering happening there.

s2k manic

O have part throttle compressor surge around 5252rpm in 6th gear with 10-+5% throttle. Stab it and it's gone. That's also with a huge air to air intercooler. I am currently installing my vmount finally and slowing the blower down 4.2 and 6.5 pulleys from 4 and 6.75. Ill post results when I can.
oh and after I added a extra idler pulley boost was 21 psi . The car made from 460 to 500whp depending on dyno . Looking to be around 450whp not trying to break the diff again or trans.