Well I have been having issues with back pressure for a while now along with afr. So we decided to pull the exhaust off and run it open dp since the exhaust was restrictive. Car is tuned @24psi. Was previously tuned @14psi with the full exhaust. Took it for a drive last night and @6,500 rpm it hits fuel cut do too over boosting. I only have a 20psi gauge still since I didn't originally plan on running over 20 so I can't see exactly how high it's going. It has a hall an mbc so we figured just turn it down and hopefully that will work. Ended up turning it 1 1/4 turn and still same issue, so I said lets just unplug it from the gate and try on spring pressure. Spring has been in there for a few years so I can't remember which one is in. Most likely a 8lb. Even on gate pressure it's still pegging the gauge and cutting @6,500. So my question is would pulling the exhaust off and having much less back pressure cause it to be uncontrollable? Any input would be appreciated.

Setup
Benson 83mm sleeved b18c
Pauter x beam
Cp 9.0:1
Super tech springs, retainers and valves
Victor x
Id1000 inj.
eBay cast log manifold
Pte 5858
Pte 38mm gate
2.5in dp
2.25in exhaust (removed now)
Tuned on s300

 

Maybe time for a new waste gate? Sounds like it is not bleeding off the exhaust gases for whatever reason, basically not opening when it should. Pop the top off that sucker and look around and double check the spring. Post pics if you are unsure.

Or your gauge could be broken?

 

If you went from a 1 1/2 to a 3" yeah itll be a big difference

Run just off the wastegate if it still spikes

Take it off and bench test it, check for leaks.

 

I'm going to pull it apart tonight and look at it. Was too hot after the pulls last night trying to sort it out. It almost seems like it's jammed closed the way it's building boost and with open dp I can't really hear if the gate is opening

 

The dp has always been 2.5" and exhaust was 2.25" so we pulled the exhaust. We are going to pull the gate off tonight and see what we can find. It was still pegging the gauge and fuel cutting at 6500 just running off gate last night.

 

im not terribly familiar with the 5858, but i know with a t3/60-1 i was unable to control how much boost i was running with a 35 or a 38 mm wastegate. it isnt able to vent the excess gases quickly enough to keep the boost at the desired level. you might need a larger wastegate or two wastegates...either/or would require a new manifold and with a sleeved block, id suggest getting away from the log manifold and acquiring an equal length of some sort.

 

Where is your wastegate positioned?

 

It's positioned between cylinders 1and2. I know it's not the best placement but it never had this issue until I pulled off the rest of the exhaust. I just purchased a top mount with a 44mm gate from a member on here so I will be changing the setup some. Would still like to get this issue solved since the old kit will most likely be going on a friends car and don't want him to have to deal with this issue aswell.

 

Minus the sleeved block and open dp this setup has been as low as 9psi and always held steady. Once I pulled the exhaust off and went open dp is when the issue started. Could it be as simple as much less back pressure?

 

dont know what to say on that..

 

Very much so. Especially at such a low boost level.

 

It's tuned at 24psi now. Even trying to just run on gate it's going over the 24psi. I'm going to a top mount manifold with single 44mm gate now. I'm hoping it will be more controllable then. I know it's not the optimal manifold for my setup but got a good deal on it and the plan is to move to a 62mm turbo at some point.

 

Your wastegate vacuum line is not getting pressure. And 62mm means nothing to us as a turbo size

 

So without vacuum on it it will just boost uncontrollably? If there is no line from the controller to wastegate wouldn't it just run on spring pressure? I know saying 62mm is vague. I haven't decided which turbo I will go with yet thinking about building the car for FIS. If I remember correctly there is a limit of 62mm. I'll have to look into it a little more to get all the specifics when I get ready to start setting it up.

 

You have a vac line from the wastegate to turbo or pre int mani right? Lol

 

I'll have to double check where it's ran from. I've never had a line from turbo to gate. The only thing I can remember off the top of my head is that the boost controller is routed to the top of the gate. It was the only way we could make more than 18psi. I'll try to go by the shop tonight and see how it's all ran. If there is no line on the wastegate at all will it not run off spring pressure?

 

Without a vacuum line the turbo will make as much boost as its capable of. In simple terms your wastegate does not open without a pressure source

 

Ok. Well I ran a line from the compressor housing to the gate it picked up some rpm from 6500 to 7300. But still over boosting. Going to let it cool down and pull the gate apart to see if there is an issue itself.

The vacuum line to boost controller is from the intake manifold, then from controller to gate.

 

The wastegate may be done for. How did this car get tuned to 24psi? Did the tuner bump up a psi at a time and what spring is in the gate? It's definitely a gate inspired issue

 

So it was on the same turbo setup on stock block. Running at 14psi for about a year. Put the built motor in and started tuning. Tried for 30psi but fuel pressure was to low so we went back down to 24 and it's always held fine. Once we pulled the 2.25 exhaust off and run open 2.5 dp the issue started. Going to pull the gate apart in about 30 minutes once it's cooled back off and see what spring is in it. Pretty sure it's an 8lb

 

It's a 6psi spring. Just got it all apart and it looks fine.

 

Well got it to run off of spring pressure but went lean so had to let out.

 

I just recently purchased a top mount manifold with an older style tial 44mm gate, I would like to know if the new tial mvr 44 spring will work with the older style gate? I searched for a long time last night and found nothing.

Also is there a point where the downpipe would be too short and mess with readings from the wideband? I just used my old downpipe cut it and turned up for hood exit to make due with what I already had. It's very short now.

 

No. They are not interchangeable. The colors and rates are different with the newer more compact designs.

As for an up-pipe affecting wideband readings. Nah, not really.

 

Thanks for the info