Boost Spikes with Full Length CAI

[Steve @ VersaTune]

For all of you with full length CAI's, I thought this might be useful info.

I was having horrible boost spike problems with my new engine. Like 22+ PSI at 2300 RPM.....
I had to temporarily use the throttle plate to keep boost down so that I could actually drive it.

I noticed that when I had the engine apart, the entire CAI pipe, TIP, turbo compressor wheel and housing, hot pipe, and even into the intercooler was covered with a mineral scale comprised mostly of road salt from driving in the winter. So, when I was testing the WGA diaphragm, I noticed that the flow from the WGA to the compressor housing was very poor compared to the spare OE turbo that I have. I found a drill bit that fits the opening of the brass restrictor that is in the nipple on the compressor housing and cleared the mineral scale from that hole.

Voila! No more boost spike.

That was caused by four years of driving with the full length CAI in Michigan.

This is the restrictor:

Turbo to WGA Restrictor

IMG_5021_800.JPG (172.16 KiB) Viewed 21585 times

DO NOT enlarge the restrictor or your turbo may not reach maximum boost.

If you are going to run a full length CAI, get a hydro shield!! Puddle sucker CAI's will cause hydro lock and the crap they suck up is not good for the MAF or the turbo.

Hopefully sharing my grief will save others from the same

[06Speed6]

What size was the drill bit that you used?

[Steve @ VersaTune]

It was too small to have the size stamped on it. The hole is about .040" or about 1mm. (Google sez ...1 millimeter = 0.0393700787 inch) The smallest bit I found at Home Depot was 1/16" which is .0625" which is too big. The bit I used was from a giant Harbor Freight bit set. Just make sure you are able to clear the opening without enlarging it. And, make sure you don't break the bit off in the nipple!

[fez]

good info!
I've been running an SRI for quite a bit, but I should probably still look into this.

[Steve @ VersaTune]

Update:

Boost Control Solenoid was also restricted due to mineral scale accumulation.

I replaced the BCS with a spare from a used turbo I bought, and it holds boost at high rpm much better.

[laxplayermjd]

so would you recommend to swap the stock air box back in for winter? or just ride with the cai. Pros and cons of each?

[Steve @ VersaTune]

Get a hydro shield for sure. That will help. It's good safety for full length CAI's anyway. It depends on your climate, use of road salt, and how ambitious you are. I hate messing with those three nuts while standing on my head and twisting my arm in unnatural positions.

An air ratchet makes that job a whole lot easier though. Mine was on for several years before it got that crusty.

[laxplayermjd]

i have a hydroshield. in memphis theres no salt used. barely snows. but i plan on going back home for the holidays to good old buffalo with the lake effect snow. I suppose it wouldnt matter for that 2 weeks times of snow and salt. Ill just clean it when i get back