When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
*Hptuners screenshots at the end show New Precision Vs Old Chinese WG with no other changes*
I wanted to share my story to help others who might have this issue as I spent a lot of time trying to find my problem.
I originally thought I had some sort of converter issue locking and unlocking causing my RPM and KPA fluctuations. After logging and figuring out my converter was unlocked during my pulls (Single Billet Disk) I moved onto other things.
I read that having my WG reference on my vacuum block with everything else (Boost Gauge, BOV, Regulator) was a bad idea. I moved my reference and also tried a larger signal line. That didn't change anything.
I swapped to just 1 spring and added my manual boost controller. I was using two springs to get 180kpa with no controller. That did change the interval of KPA fluctuation. Less spring pressure in the wastegate made the KPA fluctuations increase in interval.
I realized I had a WG issue and decided to take it off and inspect. Below is what I found. The diaphragm was kinda misshaped and the valve stem had damage from rubbing. I cleaned it up to inspect further.
I was tired of ******* with a $70 part, and decided to get the Percision PW39 wastegate. I removed my 38-44mm adapter, put the Percision WG on with the 9lb spring and went out to make a pull. KPA line is consistent and the car pulls so much better.
I learned my lesson using the Chinese knockoff WG. I'm still using a Chinese BOV, headstuds, and turbo. I hope they hold up. I made a video showing the valve stem sticking 1/2 way down, but the video is to large to upload.
Maybe I could have sanded and cleaned up the Chinese WG to make it work, but I was tired of wasting my time. I'm very happy with the Percision WG. Hope this helps.
John
Last edited by johnminer; 03-24-2016 at 10:36 PM.
Reason: Spelling
Pretty common issue. Do a little reading in here. You'll find plenty other people.
I like your Z!
I don't think I've seen many issues where the WG is sticking 1/2 way down, then closing, and repeating the cycle causing the KPA line to fluctuate like mine did.
I've seen where the gate gets stuck open or completely closed. If money is available, I recommend getting a quality made gate.
When i got my BOV's and gates from VS racing, the BOV's were real rough to travel compared to the tials i had at the shop (customer stuff)
So i tore both BOV's down and found that the sleeve that the valve stem rides in was real rough, almost rifled liked they used a drill bit.
So i spent some time with a hand file and smoothed it out and got them working ok.
With the gates, they were basically identical as a tial except they dont have nearly as much valve lift. So again, i tore them down and found that the diaphram on one of them was pinched like the one in your pic.
It still didnt open nearly as much as the tial, but probably would have caused issues.
Here is a video of the gate sticking while trying to close. I cleaned the valve stem and lubricated with anti seize prior to re-assemble and it still sticks.
They are such a simple design that it really doesn't take much to fix the "broken" gate you have. Pull the valve (make sure it's not bent) clean and debur it with some sand paper. Do the same to the bushing it rides in and use some quality high temp grease. Pop it off every year or so and regrease it and I bet it never troubles you again.... Or buy a tial which technically you should probably service every year as well. Though I don't know anyone that does.
Great info. Smooth *** looking graphs there Matt. I wonder if my synapse is being a piece of **** like this. It did sit on the shelf for years before use.
They are such a simple design that it really doesn't take much to fix the "broken" gate you have. Pull the valve (make sure it's not bent) clean and debur it with some sand paper. Do the same to the bushing it rides in and use some quality high temp grease. Pop it off every year or so and regrease it and I bet it never troubles you again.... Or buy a tial which technically you should probably service every year as well. Though I don't know anyone that does.
I agree that after disassembling the WG, it is a simple design. I spent to much time finding the problem and was mad at the part. I just wanted to replace the part and get back to racing.
flip side here are a bunch of china gate cars i did recently with zero issues all over different boost amounts
Matt, I'm happy that the rest of my "denmah kit" is working so well.
This is my first build, first turbo car, and first time tuneing anything. I'm not an expert. My entire build was based off your videos and help on the Internet.
I'm not knocking any vendor. More my lack of knowledge. Next time I'll start by disassembling the WG and inspect it when I have a boost related problem. I was ready for the problem to go away, so I bought a new part after figuring out the WG was sticking.
I'm sure the gate could be fixed, but I'm ready to run at the 1/8th now.
Hoping to get a 6.9 tonight! I'll report back if I do.
Thanks for all the help you've given along the way.
I pull the china stuff apart and inspect them beforehand. Had several with torn WG diaphragms, burr’s on shaft, poor valve face seals, metal shavings in them etc. Also use red locktite on the screws that hold the top chamber to the gate. I skipped this on my last build and the damn screws popped out a month or so after install. Not sure how the red Loctite holds up to the gate heat, but I’ve never had one come apart on me since doing this.
If you put a little extra effort in on the cheapie gates and maintain them I’ve yet to have one fail. I ran the same china gate for 8 years on my black rx-7 still working when great when I sold it.
E85 also seems to chew them up fast with all the extra water in exhaust. I’m gonna lube my WG up this weekend now that I think of it!
I have 2 vs racing gates and a bov from them, they look great inside and have worked perfectly. 220 bucks or whatever later for two 44 gates works for me
I check my knockoff 44mm pretty often. I also grease the shaft with some high temp and work if back and forth into the guide. It controls boost down to 5 PSI with zero issues.
I've had true Tial wastegates stick on me before and this same clean/grease trick did the job. Its seems pretty common sense to check them every year or so, especially if they are whats keeping your engine alive.
I appreciate the feedback. I'll hang onto the gate and might use it in a future project. When I get some free time I'll cleanup the valve guide.
On a positive note, I ran a 6.9 at 102 tonight with a 1.73 60ft! I did the SYTY shuffle on the line and it helped me build 1-2 psi on my footbrake. I pushed through the brakes on my other runs and only got a 2.0 60ft. Still trapped over 100.
I'm very happy with the "denmah Kit" results. Maybe I'll try the 4L80e 3rd gear mod trick.....not sure the 10 bolt will like that. Lol
My Tial knockoff just caused me to overboost for the 3rd time. 30 PSI.
Took it apart, turns out I didn't push the diaphragm all of the way back in when I was putting it back together. My fault. Good news is, the Tial MVR diaphragm assembly is $44 and they are local. They are also a direct fit.
At least a American company can get something out of it.
China makes very little off of the knockoff parts they sell, at least in dollar amount (Percentage wise, they make a good profit). Most of the profit goes to whichever American company is actually selling them.
Those eBay fabricated intakes can be imported from China with rails and throttle body for $120/each. The full setup with throttle body is then typically sold for $599-799, with a majority of the profit going to the US.
03-24-2016, 10:15 PM
Bad 44mm Chinese Wastegate 
