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B21FT TD04HL-15G increase boost to around 10psi

ogamer777

ogamer777

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Joined
May 22, 2016
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New North Winchestersonville (PNW 425 gang)
As the title states the engine/turbo combo is b21ft with a 15G. I just installed a calibrated boost gauge to replace the cosmetic OEM boost gauge. The new gauge shows that I am capping out at 3.5-4psi. The 244 was originally non-intercooled turbo, but I have the complete intercooler setup installed already. So now my question for you guys is, how to I up the boost to 10psi? If it's a matter of installing a manual boost controller, then I am a little confused on how to install it. I have one that didn't come with a check valve. It came with instructions, but they are vague. They also show two different diagrams. One shows to remove the short vacuum hose from the turbo outlet port/wastegate, and put the MBC inline with that hose so the MBC acts as a T of sorts. I've read a lot of different methods to install the MBC, some that contradict the MBC's installation instructions. So with all that said, I wanted to see what you guys who have installed an MBC on your B21FT did for MBC install.

I also tried preloading the wastegate actuator rod. I did two complete turns towards the wastegate. Apparently, no gains occurred. Thanks for your help.
 
Pics of boost controller? 3-4#, leak check it, hot side and cold side. Wastegate preload of about 1/8”-1/4” and you should see something a little higher, 7# ish.
 
Edit: I got this completely backwards from memory as ZVOLV pointed out below.

The wastegate actuator pulls the wastegate shut with spring pressure and pushes it open when manifold pressure is applied. So you want to make the arm shorter to pull it shut harder. Longer will make it open sooner.

Easiest way to set base boost without the MBC is to put a pump and gauge on the wastegate actuator.

Pump it up to just below the boost pressure you want to hold, like 9 psi in your case, then turn the rod end so that it drops on to the wastegate arm while you hold it closed.

Then when you release pressure, you'll pre-load the wastegate. It should have significant spring force holding it shut, and not open till the manifold pressure pushes it open at the PSI you set on the gauge.

Test drive. If your dash gauge differs from what you want, adjust it a little from there.
 
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on the older 240's I believe they had an overboost cutout switch, it was in the engine bay if I recall, as the 2.2 740's had it under the dash.
 
It's under the dash on 240's also. It's connected to the same hose that goes to the gauge. The switch on the firewall is for boost enrichment.

240OverboostSwitch.jpg


The pressure given is for B21FT w/intercooler. Cars without an intercooler used a switch that cuts out the pump at 10 psi. Make sure you have the correct switch.
 
hiperfauto said:
It's under the dash on 240's also. It's connected to the same hose that goes to the gauge. The switch on the firewall is for boost enrichment.

240OverboostSwitch.jpg


The pressure given is for B21FT w/intercooler. Cars without an intercooler used a switch that cuts out the pump at 10 psi. Make sure you have the correct switch.
Click to expand...

Very helpful. Thank you. I totally spaced the over boost switch. I bought an IC one a while ago. Simple plug and play. 14.9psi is the highest boost THAT WILL NOT DAMAGE ANY COMPONENTS correct? The original motor has around 235k.
 
I believe the intercooler system used a relay to energize a boost control solenoid that would allow more boost over 3700 RPM. Under 3700 rpm boost is limited to ~8 psi.
 
hiperfauto said:
I believe the intercooler system used a relay to energize a boost control solenoid that would allow more boost over 3700 RPM. Under 3700 rpm boost is limited to ~8 psi.
Click to expand...

I think you're right. I was talking to Laughlin about it. IIRC it is something in the engine bay that limits boost like you said. I don't have that since my car was not an original intercooled car.
 
There isn't a magic psi number that will be safe. I pinged my b21ft running right around 14-15 with a 15g. AFR was fine, timing was not - even with the mechanical timing mod. Fwiw.

ogamer777 said:
Very helpful. Thank you. I totally spaced the over boost switch. I bought an IC one a while ago. Simple plug and play. 14.9psi is the highest boost THAT WILL NOT DAMAGE ANY COMPONENTS correct? The original motor has around 235k.
Click to expand...
 
turbochimp said:
There isn't a magic psi number that will be safe. I pinged my b21ft running right around 14-15 with a 15g. AFR was fine, timing was not - even with the mechanical timing mod. Fwiw.
Click to expand...

That's unsettling. I'm going to be installing a v or vx cam as well as adjustable timing gear. I hear people advancing timing 5? is the go to setting, this I would imagine helps prevent the pinging?
 
Adjusting turbo pressure with wastegate preload is kind of a waste of time.

Get the WGA set right, and pop on an MBC, not only will you be able to adjust boost, but spool time can be dramatically improved by going to a boost controller of some form.

I would set the WGA a few psi below target and let the mbc do the rest. You can set the WG pressure with a bike pump setup. Or pop it all together and go for a rip and see where everything lands.

Hook it up like this.

5483.jpeg
 
Uncleknucklez said:
Adjusting turbo pressure with wastegate preload is kind of a waste of time.

Get the WGA set right, and pop on an MBC, not only will you be able to adjust boost, but spool time can be dramatically improved by going to a boost controller of some form.

I would set the WGA a few psi below target and let the mbc do the rest. You can set the WG pressure with a bike pump setup. Or pop it all together and go for a rip and see where everything lands.

Hook it up like this.

5483.jpeg
Click to expand...

Yep. That's how I've got it set up now. Got it dialed in at around 8psi. Once I install the intercooler over boost switch, I'm gonna aim for 14-14.9psi.

Might be a dumb question, but, is there a way to install an electronic boost gauge with stock k jet? Would be nice to set the boost limit and go, as opposed to setting it, test drive, set it, test drive, set it, test drive etc
 
EBC will absolutely work with Kjet, an MBC will be fine, but I am with you, having a "set and forget" approach is really a nice way of doing it, I want to add an Innovate SCG-1 to my car at some point in time.
 
ogamer777 said:
Yep. That's how I've got it set up now. Got it dialed in at around 8psi. Once I install the intercooler over boost switch, I'm gonna aim for 14-14.9psi.

Might be a dumb question, but, is there a way to install an electronic boost gauge with stock k jet? Would be nice to set the boost limit and go, as opposed to setting it, test drive, set it, test drive, set it, test drive etc
Click to expand...

If you are concerned about engine damage, I would advise against going to 14 psi on that setup. The cam adjustment you mention changes cam timing for valve events - not ignition timing. It has been my experience that the mechanical ignition retard on the b21ft is not sufficient to adjust timing enough in the 14 psi range with that turbo. I had also used an additional shim to increased fuel pressure. Maybe your stuff will react differently.Also bear in mind that boost will likely spike quite a bit above your WG/MBC setting on initial boost. On my first worn out 15g, I saw spikes of 3-4 psi.

I would recommend that you do some reading on the basics of pre-detonation. Given how variable kjet fueling can be from car to car, I would also install a wideband for AFR readings. Fuel is only half the equation though - ignition timing is the other. There are some writeups on how to install det-cans on this site too. 10 psi on a kjet/15g is probably fine. Either way, your going to learn about this stuff. Learning by melting stuff is fine, but can be inconvenient.
 
Just to add to the mix. The generally accepted level of boost with stock stuff which is what you have besides the 15g is about 11-12psi. Which is still a lot of fun. Especially with a faster spooling turbo like that. Another issue in my experience is the stock intercooler end tanks will start to leak over time with boost much over that same 11-12psi.
 
Thanks guys.

Not terribly concerned about engine damage at all. Worst case, I have a b23f I can toss in. It's my DD but my commute is less than a mile.

With that said, I will stick to safer boost ~12psi. At least for the time being. Already noticed the boost spoke with the current setting. Was considering an AFR wideband setup as well. But I've read you maintain the oem o2 sensor as well? And with kjet, the AFR isn't like efi cars, so not 14.7 or whatever optimum AFR is, correct?

I do want to swap in a B cam, and was eyeing the KL racing / do88 intercooler. I know the IC will help out. But will the cam help or make a difference to anything in this equation?

Again I appreciate you're input here.
 
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