Let me start of by saying this is on a G35 not a RX7 but that I know this is one of the only places I can get some decent opinions on this and its a turbo problem so the engine isnt really all that realitive. Also I really dont have any idea what turbo it is because you cant really see it good when its in the car....its supposed to be a GT35R but with "custom" compressor and turbine housings that APS made (its an APS kit). They wont release any kind of specs at all except that its ball bearing. This is a internally wg kit.

Here is the problem...and its the same with a electronic or manual boost controller we have tried both. The boost will steadily climb then when you hit around 4000-4500rpms it starts to drop. If I turn up the controller the boost will go up but it always starts to fall on its face around 4500ish and had droped in half by redline. We had tested the pressure side and it seemed like it was holding pressure.

Here is where it starts to get weird...
Last night we disconnected the wg actuator and wired the flapper closed, it would barely even build boost at all, I got up to about 3psi by redline and that was it didnt even get into boost till probably 5000 rpms. That is with the wg wired closed....basically NO wg at all....we also capped the bov just to make sure it wasnt leaking or something....still the same. At that point I'm thinking damn the turbine side must just be choking the hell out of the engine.

Soooo, we go a head and leave the wg wide open flapping in the breeze, most cars can build boost with it like that so I'm thinking hell if the turbine side is choking from back pressure she wouldnt have any problem building some boost with the wg wide open. It will be laggy but it should make some boost. HELLLL NO....the boost was basically exactly the same no matter if the wg was wide open or wired closed. It wouldnt get into boost till about 5000rpms and it would gradually go from 0psi at 5K up to about 3.5psi at redline 6500ish.

At this point I'm thinking, alright it has to be a pessure side leak but there are only 3 connections it could be and they are all very tight and making a good seal. The bov has been capped this entire time so thats not the leak. The only thing could either be the IC has a leak or something is up with the turbo.

Here is the other twist. So we get back home and he hooks his actuator back up with my manual boost controller....bam back to how it was before where it will actually build boost, its much more responsive and builds boost better than with the wg wires shut BUT it still starts gradually dropping its boost to where its lost half of it by redline. Its going up to 9psi by 4000 and starts dropping down to about 4psi by redline.

Alright....anyone want to make some comments? I think we are fixing to pull the turbo off, take it to BNR and have Brian inspect it. Might also pull the IC and have it inspected/pressure tested. Maybe its just a bad turbine AR selection, I have no idea what size AR or even what turbin wheel is in this turbo since APS wont say anything.

Comments? Questions? Anyone want to point out something I might be overlooking? Give me some ideas? lol

Oh yea, one last note...they sold about 25 or so of these kits in a initial group buy and everyones is doing this. APS is making up BS excuses saying the kit was designed like that...we all know this is total bull ****. They marketed the kit as building 9psi right out of the box and even show a boost graph hitting 9psi by around 2500 and holding it to redline. I think they changed some turbo specs after thier demo car without testing it, screwed up, and dont want everyone to know it. Thier demo/test car has pics of the turbo with Garrett stamped into the compressor housing...the kits dont. I think maybe they changed some turbo specs after designing the kit and its not working the way they thought it would and they dont want to fix it since they sold the kits cheap in a group buy. We shall see!!! And yea, they dont want to help anyone or even talk to anyone about this problem anymore. This official stance it is was designed to do that to be safer for the engine.....******* liars. OK...rant off....this really frustrates me.

Can someone give me some ideas.

Stephen

 

Stephen, the shop next door to me just installed this kit on a g35. I watched them install it at various times over the last couple days. This is the single turbo kit with the cross over pipe correct? It also comes with a scavenge pump to get the turbo return oil back into the pan. It comes with a large oil pan and upgraded fuel pump. If this is the same kit, I know that the car just came back with some issues. The guys at the shop said they were impressed with the stuff that came in the kit but the car didn't feel all that impressive. Maybe they are having the same problem.

The car is there now. I will talk to Charles and Taylor tomorrow to see if your problem is the same as what they are experiencing.

I will keep you posted

Mike

 

Yes, this is the same kit. Everything looks real nice but they wont release any specs on the turbo and it seems like most of the kits are having problems holding boost. And ASP is basically just blowing people off and telling them its supposed to do that for engine safety (total BS) lol

Keep me posted man....any info you can find out would be GREAT

Stephen

 

damn dude, this makes no sense??? Internal WG wired shut and you can only build 3psi

I don't really have any guesses, never worked on a single turbo Z33 or VQ35 motor...

I take it, you can't hear any exhaust leaks...
plumbing for V engines for single turbo seems tricky and not very efficient, so inspect that before you pull the turbo off.

 

Stephen, there is a thread going on in the 350z forum on the car next door. Evidently everybody is bashing the shop because the kit is not all that it's craked up to be. I sent them the link to this thread so they could post it to help shed a little light on this situation. The peolpe on the 350z board seem to be a bunch a know it alls. Tough crowd. I thought the guys next door could use a little back up.

Evidently there are some issues having to deal with the CAS light coming on and the car having hard starting problems. APS ships a piggyback computer/chip and a new wire to tap into the CAS. There seems to be a problem with their wiring harness. The car also has the SLP light on as well if I recall. They were also comenting on how loud the car is and how it should be quiter with a turbo, that it must have exhaust leaks. I guess it doesn't matter that the kit removes all of the CATs and has a 4" down pipe Also did your kit have problems with the exhaust hanging too low. This kit needed to have the exhaust cut and rewelded in one place to raise it up.

The turbo is also a t3/t4 foot print. not sure if it is a gt35r or not. I am a little suprised on the boost numbers quoted though. 9 psi on a 10.5 to 1 motor. I would think that the kit would be 4-5 psi. Are you sure of this 9 psi claim. Also This kit is technically for a 350z correct? I know the intercooler placement ends up being covered by the pumper. Also the g35 doesn't have the hole for IC piping to run through. Did you have to cut this as well?

Mike

PS any luck trying to set up a oil pressure regulator to limit the oil pressure going to the turbo on the RX7. I am getting my motor back together and want to implement a setup like this. I want to limit the the feed pessure to 55psi. Do you know of anything to use?

 

Just to shed a little light on some VQ35 stuff. At 10.3:1 compression yes this motor is a pain to boost. However that 9 PSI number is correct. Most twin turbo kits come at 5-9 PSI out of the box and both single turbo kits are above 8 PSI. I don't have the kit in quesiton I have the other single turbo kit by Turbonetics. As mentioned the boost drop is a mystery. No other kit on the market does that. My car runs 8.5 PSI daily and the boost doesn't ever drop. The twin turbo kits are the same. The APS kit does in fact place the intercooler behind the bumper and does not make changes to the bumper so air flow is minimal. To combat this Turbonetics added twin Spal pusher fans on the intercooler to ensure airflow gets to the intercooler and so far they have seen a cooler charge then they saw on the Z with just forced air under acceleration. The primary reason there of course being that the fans are running when the car is not moving while the Z gets no such advantage. As for the management piggyback no one really knows what parameters are entered as APS locks the unit and the only way to tune it is to send it or drive the car to an authorized APS dealer where they can dyno tune the car. As for "loudness" its true the kit does remove all the cats but even on my car with no cats the exhaust is not much louder then before. Then again I'm sure much of this is going to be dependent on the exhaust this guy is running. The APs kit was originally designed for the Z but a supplemental kit for the G should have been included with the necessary changes to make it fit. There isn't much that has to change as from the radiator support to the tranny the car is damn near identical. Hope that helps out in trying to figure out the issue.

 

Thanks for the info. I also thought that the setup could stand to have some spal fans to help flow through the intercooler. You said that you use pusher fans. This would mean that they are located between the bumper and the IC, correct? Is there room for fans between the IC and radiator? As for the exhaust, I am not sure. I think it has a cat back but not sure of the brand.

Sucks though about the boost problems. Could it be caused by the map? Maybe a sensor telling the ECU to back out timing or something.

Mike

I will see if we can get some boost readings when/if the car comes back.

 

No there wasn't any room behind the intercooler to get fans due to the kit ensuring the front bumper bar is retained. So they basically had to go in front. Of course they are set up so that if you get an aftermarket front bumper you can remove the fans and flip around the intercooler to hide the fan mounts and it looks like it was made like that. As for the tune being the cause. That was what APS originally said. That they had programmed boost control into the piggyback to scale down the boost above 4500. This was proven false when the manual boost controller was used. Then they said it was exhaust back pressure but I think the car in question actually removed the exhaust after the supplied downpipe and it still did the same thing. So now we are at this point where nothing that is logical seems to be the answer.