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Finnally getting some seat time with my 87 TA. 5.3, ported stock heads, 218/228 custom cam, NNBS intake. CX racing single turbo kit, 76/65 .81AR journal turbo, 3” FMIC and water meth. All controlled by a FItech LS EFI system.
Data logs showing max boost of 142kpa. It comes in early and sticks around all the way up to 5k+. I pulled the CX racing 60mm WG and hooked it up to my compressor and with a regulator my WG spring started to move around 12-13psi. Fully open alittle after that. I opened it up and it has the biggest spring available in the box, 2 smaller springs in the box. I got a good bit of boost leaking past the valve guide in the WG. My WG is hooked right up to the compressor on the turbo as well.
So is it safe to assume that my 12psi spring is only letting 6psi and that I have 2:1 backpressure in the hot side? Figure 12psi cut in half would be 6psi or 142Kpa no? So to crank this thing up I need to increase spring pressure right? I added the next larger spring which pushed cracking pressure to around 25psi. I figure if I half the spring pressure psi that should be my boost right? I would like to be around 10-12psi as I was running about that with my supercharger.
My only other thoughts are a massive boost leak (WG stem) or backpressure in the exhaust. Which is 3” Downpipe into a 3” catback with no cat.
It doesnt seem to leak out the top top of the WG and I’ve read that leaking around the shaft is normal.
If your wastegate or controller is referenced to the turbo it will not compensate for any losses due to the cold side, specifically the FMIC. That is why you usually reference it to the intake manifold. If your intercooler sucks and drops 3 psi, that's 3 less psi of boost the car will see. You pressure test the cold side for leaks?
If your wastegate or controller is referenced to the turbo it will not compensate for any losses due to the cold side, specifically the FMIC. That is why you usually reference it to the intake manifold. If your intercooler sucks and drops 3 psi, that's 3 less psi of boost the car will see. You pressure test the cold side for leaks?
yes I realized that. I read that referencing to the compressor was better to kee turbo over spooling to a minimum. But yes I agree. It’s a 12x31x3” with 3” inlet/outlet, eBay special. Not the best but not going to spend a ton on it. I didn’t measure pressure drop but I didn’t test the cold side since the turbo. The cold side was 90% untouched from the supercharger setup and that was pressure tested and held boost with no leaks to like 20psi.
you have the ffire ring installed that was my wg issue i had
the waaat?
if your asking about the locator ring for the valve then yes it’s installed. CX uses a 1 price locator/flange to put pressure on the flange and the valve. It makes installing the WG a PITA lol bc I need to compress the valve to get it to close enough to get the vband on it.
yes I realized that. I read that referencing to the compressor was better to kee turbo over spooling to a minimum. But yes I agree. It’s a 12x31x3” with 3” inlet/outlet, eBay special. Not the best but not going to spend a ton on it. I didn’t measure pressure drop but I didn’t test the cold side since the turbo. The cold side was 90% untouched from the supercharger setup and that was pressure tested and held boost with no leaks to like 20psi.
You want more boost which will spin the turbo harder anyways. Moving the reference to the intake can help with spool as well. I'd move it first and then see about swapping springs .
if your asking about the locator ring for the valve then yes it’s installed. CX uses a 1 price locator/flange to put pressure on the flange and the valve. It makes installing the WG a PITA lol bc I need to compress the valve to get it to close enough to get the vband on it.
So I guess a better question is... does a WG spring that opens at 12psi on the air compressor correlate to 12psi of boost? Seems like it wouldn’t no? Due to pressure on the valve of the exhaust in the hot side pushing on the valve along with the boost from the compressor. I assume my hotside is under higher pressure due to the small 65mm exhaust side.
So I guess a better question is... does a WG spring that opens at 12psi on the air compressor correlate to 12psi of boost? Seems like it wouldn’t no? Due to pressure on the valve of the exhaust in the hot side pushing on the valve along with the boost from the compressor. I assume my hotside is under higher pressure due to the small 65mm exhaust side.
id def reference after tb to see true boost reading and my tubro 7875 with 3 in dp and exhaust
So I guess a better question is... does a WG spring that opens at 12psi on the air compressor correlate to 12psi of boost? Seems like it wouldn’t no? Due to pressure on the valve of the exhaust in the hot side pushing on the valve along with the boost from the compressor. I assume my hotside is under higher pressure due to the small 65mm exhaust side.
the pressure inside your manifolds will have very little effect on the opening of the valve. You are correct in testing with the air compressor. Too restrictive of an exhaust can limit your boost pressure. A single 3" pipe is good for a max of around 600HP with a dumped WG. So if you're over 500 ish to the wheels that is a restriction for you.
Too large of a wastegate will cause this issue as well. A 60mm wastegate opened only 60% will bypass as much exhaust as a 38mm gate opened 100%. So the gate would only need to see enough boost to crack open in order to keep boost from climing.
Which springs did you put in the gate? They aren't made to be ran individually. In order to get the boost pressure that the highest spring is rated for, you must run all 3 springs.
Wastegate is plumbed right off the compressor with 1/4” silicone line. My BOV is run from a vacuum block along with my innovate PSB1 which is a wide band and boost gauge with AFR failsafe. This is my primary vacuum and boost gauge. The FItech system uses a 3bar map sensor that reads 99.5kpa with EOKO. They have been tested and read correctly up to 285kpa. So the wastegate was fed off the compressor housing and the WG was running the single large spring which tested to crack at 12-13psi and fully open by 14-15psi. I was testing that with a 15psi fuel gauge in-line from the compressor regulator. The top of the wastegate is vented to atmosphere so it’s running just off the spring with the bottom referenced to the turbo compressor. My BOV is a eBay tial 50mm copy and I trimmed the spring to open alittle above 15” or vacuum. I only pull 13-14” so it’s closed at idle, but the original spring needed like 21” before it opened and was stiff as hell. I read that the spring should be slightly higher than idle vacuum.
With this my logs show 142Kpa and it builds slowly starting around 3k.
I have a voodoo MBC with a ceramic ball upgrade that I can put on but wanted to get a base for mysetup before and if it’s even needed.
So there are 3 springs, small, medium and large. The large spring it was gave me 12psi. Large and medium spring together gave me about 25psi so that means the medium spring is about 10psi. I didn’t test the small one.
So in fear of overboosting with the double springs I decided to remove the double springs and go back to the single large spring. The large spring and WG I have removed from the turbo compressor housing and tapped into the 1/4” silicone hose for the BOV. So they are now Tee’d together, the line runs back to my boost/vacuum block which is fed from the brake booster port on the intake. The MAP sensor is in the stock location at the top of the NNBS intake. I want to see what boost it makes now that it’s referenced to the intake. I worry now that the WG valve will create a vacuum leak as it leaks a good bit with pressure pushing through it. The difference in boost will provide me with pressure drop as well since I know what boost it was making pre intercooler.
I was making 9-10psi with the supercharger on the same cold side before he turbo and intake swap. So the cold side can handle more pressure for sure, I use real USA clamps and everything is cranked down.
Here is a pic of the new lines that I just ran. But you can see turbo placement and WG placement. The WG was def opening because I could see the carbon trail and some slight leaks at the dump vband. Also the inside of the WG had black exhaust running through it. Personally I like the idea of running a low pressure spring and then cranking it up with a MBC bc if something fails it will go back to spring pressure.
Idk what’s going on with ls1tech but pics load but aren’t shown.
Here is 2 more pics for you guys. One shows the full layout of the system so you can see everything. The 2nd pic is the log showing RPM, MAP, COOLANT, AFR etc. all logs start with me in 3rd gear and rolling into boost. Anything in the 20% throttle starts to put me into boost. Starting as early as 3k Rpms. I haven’t logged or tested anything manually shifting from 1st to 2nd or 2nd to 3rd. I’m sure from a dig and heavy throttle the boost could come in sooner and harder. But boost peaks around 138-140kpa and hovers in the 138-142Kpa through the 3-5k range so that means the WG is adjusting boost to 6psi.
the pressure inside your manifolds will have very little effect on the opening of the valve. You are correct in testing with the air compressor. Too restrictive of an exhaust can limit your boost pressure. A single 3" pipe is good for a max of around 600HP with a dumped WG. So if you're over 500 ish to the wheels that is a restriction for you.
Lots of BS here. I've had a setup that would blow the waste gate open on back pressure alone, mind you it was a very poor setup. My L33 made just over 800 wheel on a full 3" exhaust and made 25 more with the cutout open.
Have you performed a boost leak test? You need to check this for sure. You might be surprised at what you find. You could block off the BOV for a pull. Reference the gate off the intake and try again.
Lots of BS here. I've had a setup that would blow the waste gate open on back pressure alone, mind you it was a very poor setup. My L33 made just over 800 wheel on a full 3" exhaust and made 25 more with the cutout open.
Have you performed a boost leak test? You need to check this for sure. You might be surprised at what you find. You could block off the BOV for a pull. Reference the gate off the intake and try again.
by a poor setup do you mean... like a 76/65 turbo? Lol. I know mine is less than idea but I wanted fast spool and 6k max so I think the 76/65 will get me there. But I have a 78/75 and GT45 new and sitting on the shelf if need be. I thought I read that a 3” DP would support a lot of power. Leaving alittle
on the table but the 76/65 and 76/75, 78/75 all have 3” vband exits.
Boost test was performed from the cold side start to the pipe that meets the TB. No leaks up to 20psi. I can’t boost test into the intake or though the turbo due to leak down in the engine. But I did test the cold side and it passed. I can hear the BOV open tho it isn’t very loud which is why I suspected low boost even before seeing the logs. But now I know the wastegate leaks around the valve guide a good bit so that’s bleeding boost/vacuum. It could seal up better when it heats up and I hope it does.
My honest guess is that since I referenced to the compressor housing it was seeing boost quickly since spool is quick and at a low rpm, coupled with the small 65mm exhaust wheel it’s increasing the back pressure which pushes the valve open. But since I was running on just spring which opened at 12psi my guess is that coupled with boost and exhaust pushing the valve open plus that I was referencing the compressor (pressure drop after perhaps) seems like I lost 1/2 my pressure. Given a possible 2:1 exhaust pressure to boost ratio it could make it plausible I wouldn’t get 12psi on the spring alone.
I changed the WG reference to the intake so hopefully that fixes it. Should be interesting to see the change in data after referencing from the intake vs the compressor.
Stacking 2 springs to get 25 PSI is definitely not right. Stacking all 3 gave me 15 PSI.
Don't use the regulator attached to your air compressor to determine the pressure that the gate opens. You need to T into the line going from the air hose to the wastegate and put a boost gauge or your MAP sensor on it.
Stacking 2 springs to get 25 PSI is definitely not right. Stacking all 3 gave me 15 PSI.
Don't use the regulator attached to your air compressor to determine the pressure that the gate opens. You need to T into the line going from the air hose to the wastegate and put a boost gauge or your MAP sensor on it.
I wasn't using the regulator as my gauge. I used the regulator to apply 0psi up to where I wanted. I used an inline pressure gauge to verify the cracking pressure. Basically the same system I use to pressure test my cold side piping. Its basically a 1.5" 15psi fuel pressure gauge Tee'd into some silicone hose with a compressor quick disconnect on the end. Plugs right in and I can adjust pressure with the compressor regulator. When I stacked 2 springs I had to replace the 15psi pressure gauge with a larger one to test the 25psi open pressure.
04-15-2018, 08:48 AM
School me on my turbo boost issues 
