I've been getting boost spikes whenever I go WOT and thought of this easy fix.

First I bought an aluminium Radiator Filler Neck by Moroso:

MOR-63486 $30 CDN



Then I bought a 13psi Radiator cap from Walmart for $5 CDN:



All you need to do is drill a bunch of holes all around the side of the filler neck and weld it onto your charge pipe or intercooler. Since the neck is aluminium you can either buy a small length of aluminium pipe & hose clamps to insert it into your charge piping or weld it directly onto your intercoolers end tank. I welded mine right onto the back side of my IC's inlet tank. Then you just twist on the cap (not all the way, just half way so it holds the spring down tight) and bingo you've got a safety air-bypass.

They sell the radiator caps in a bunch of different psi settings: 7psi, 13psi, 16psi etc.

So if in the future you want to increase the boost, just buy the next rad cap up and your set. I have my MBC set to around 12.5psi so when I smash the gas the boost fly's upto 13psi and comes down to 12.5. Just incase something happens to my wastegate line I won't blow up my engine because this rad cap will bleed off all the extra boost past 13psi. I'll post up a picture of the actual cap installed tommorow.

PS: you don't want to turn up your boost controller past the rad caps psi because it will cause your turbo to spin faster than it needs to be, causing its efficiency to drop.


Modified by phresh_5 at 10:45 AM 6/13/2005

 

wow, very clever design. that deserves a bump.

but may i suggest, if you're getting boost spikes. atleast figure out the source of the problem.

 

My T25 likes to make boost so fast that it passes the psi that the wastegate is set to. For example to get it to stay at 11psi it would initially spike to 14 then settle at 11 to redline. Since now I want it to stay close to 12.5 I'd rather make this rad cap than have it spike to 15.5 and settle to 12.5.

But anyways, thanks for the bump

 

the T25 is smaller than the Mitsu 15G right? thats what I got, 15G. It spools quick for me as well...

 

How bout those pics?? Very interested to see this setup on the car

 

Not a new idea, they used to use these instead of wastegates That Mike B. guy at MRP with the 260Z is running his turbo this way (no wastegate). He shims the cap to get more boost

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by raene &raquo;</TD></TR><TR><TD CLASS="quote">Not a new idea, they used to use these instead of wastegates That Mike B. guy at MRP with the 260Z is running his turbo this way (no wastegate). He shims the cap to get more boost </TD></TR></TABLE>

That's crazy! sweet

Mention this on HMT and everyone will do this instead of buying an expensive Wastegate...haha

 

yes pics. another good idea from a fellow canadian!

 

you could also cap the turbo end of the intercooler piping and pressure test the system really easily?!!??

 

i have also seen these on a set up as a type of BOV as well, this old dude in my area he is like 68 years old, he did a turbo v8 in his truck and has these on the charge pipes, works well and is actually loud as hell

 

problem with using this instead of wastegate is youll overspin the turbo and decrease the life expectancy.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by project dc2 &raquo;</TD></TR><TR><TD CLASS="quote">problem with using this instead of wastegate is youll overspin the turbo and decrease the life expectancy. </TD></TR></TABLE>

bingo!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by project dc2 &raquo;</TD></TR><TR><TD CLASS="quote">problem with using this instead of wastegate is youll overspin the turbo and decrease the life expectancy. </TD></TR></TABLE>

I don't think that's true... it's still encountering resistance, it's not like the charge pipe is disconnected.

He's been running this setup for years and going faster and faster, so far no problems with the turbo's lifespan, currently he hits 18psi.

 

very intresting postpics of this on your car

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by raene &raquo;</TD></TR><TR><TD CLASS="quote">

I don't think that's true... it's still encountering resistance, it's not like the charge pipe is disconnected.

He's been running this setup for years and going faster and faster, so far no problems with the turbo's lifespan, currently he hits 18psi. </TD></TR></TABLE>

does he drive the car everyday ?

oh yeah. the old school 300ZX runs valves liek this. its called a pop off valve.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by adseguy &raquo;</TD></TR><TR><TD CLASS="quote">That's crazy! sweet

Mention this on HMT and everyone will do this instead of buying an expensive Wastegate...haha </TD></TR></TABLE>

hahaha he will be very popular....

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by project dc2 &raquo;</TD></TR><TR><TD CLASS="quote">
does he drive the car everyday ?

oh yeah. the old school 300ZX runs valves liek this. its called a pop off valve. </TD></TR></TABLE>

Used to. He only drags it now.

After thinking about it, it probably will overspin a turbo that is nearly maxed out on a setup, but not otherwise.

This would be a cheap and super easy way for people having boost creep problems to solve them without welding on another wastegate Imagine a full-race kit with a rad cap on the charge pipe, haha.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by raene &raquo;</TD></TR><TR><TD CLASS="quote">


This would be a cheap and super easy way for people having boost creep problems to solve them without welding on another wastegate Imagine a full-race kit with a rad cap on the charge pipe, haha. </TD></TR></TABLE>

I would love to see that.

 

I suppose this could replace the BOV and wastegate on a really ghetto setup, couldn't it?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by raene &raquo;</TD></TR><TR><TD CLASS="quote">

Imagine a full-race kit with a rad cap on the charge pipe, haha. </TD></TR></TABLE>

LOL

 

just imagine unhooking your wastegate line... what happens
same thing here its just you dont have the increased boost seen at the intake manifold

so the turbo will spin faster and faster until it reaches the maximum speed the exaust gases will spin it

imagine this scenerio on a stock turbo'd car... boost increase until something gives this is why many turbo cars have fuel cut

quick explination, pm me and i'll get into detail

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by adseguy &raquo;</TD></TR><TR><TD CLASS="quote">

That's crazy! sweet

Mention this on HMT and everyone will do this instead of buying an expensive Wastegate...haha </TD></TR></TABLE>


Actually most of us on HMT use turbos that come with internal wastegates so having to buy a radiator cap is out of the budget

 

Will that thing be able to vent enough air to make a difference? The pop off valves used on indy cars for example are huge:



Big spring loaded thing on the right side of the intake plenum.

 

Greddy makes this same type of thing...it's a relief valve so in case of an overboost it bleeds off air. The radiator cap thing is pretty resourceful but really it's inefficient and isn't needed unless you're living in the 70s and don't know anybetter. good idea though.

 

You'll probably need 4-5 of them to make the funtional, or at least work effectively.

I see most guys use a piston-type blow off valve and place an appropriate spring so that it will "blow off" at a certain pressure. The BOV's are much larger and will flow more than enough to work as a pop off valve.