Mr rx-7 tt

iTrader: (5)

On a 1987 TII with stock injectors and fuel system is it safe to throw on a FCD and make 10 psi ? The reason I ask is the car already has a downpipe and is spiking to 10 psi and hitting fuel cut. If it's not safe I will just restrict the exhaust flow more.

Thanks in advance.

NZConvertible

Fuel cut is at 8.6psi. If you want 10psi you'll need a FCD and an upgraded fuel pump. The injectors will be fine.

Don't restrict the exhaust, that just makes the turbo and engine work harder to get the performance you want. Remove the turbo and port the wastegate so you have proper boost control. 10psi with a ported wastegate and open exhaust will give you more power, make less heat and use less gas than than 10psi with a stock wastegate and restricted exhaust.

My wastegate porting: https://www.rx7club.com/2nd-generation-specific-1986-1992-17/serious-s4-wastegate-porting%85-343788/ (scroll down for the reposted pics)

dirtdox

That's nice work on the wastegate. I did a search on porting recently but didn't see that. Very good info!!! I have my turbo off now. Looks like a trip to my neighbor's shop to use his mill. Do you still have the twin scroll system hooked up on the manifold?

Funkspectrum

iTrader: (5)

I removed the twin scroll system and ported out the turbo runners to the same size...

works great!

dirtdox

Thanks! I think i'll do that also. Is there a noticeable amount of lag afterwards?

Mr rx-7 tt

iTrader: (5)

I actually want to make less boost as it is an older dudes car. He left it with some shop which put on a dp and and air cleaner. I put the stock airbox back on which dropped the boost down and I am now still getting 10 psi/fuel cut. I would like to drop it down to 8 psi.

SureShot

Like they said above - the waste gate port job is his main need.

Right now - the ECU's fuel cut may be all that's saving this motor from creeping into the danger zone.

Mr rx-7 tt

iTrader: (5)

According to Racing Beat all that is needed is FCD. They said if the intake is stock and everything else is stock other than the dp then 10 psi is ok for the stock fuel system...

SureShot

At 10 PSI in cool air, you're right on the hairy edge of detonation.
Unless this engine has been rebuilt with 2-piece seals, all it takes is one knock.

BTDT

Mr rx-7 tt

iTrader: (5)

It's just been rebuilt with two piece seals. Maybe I'll suggest a TT pump to the guy.

Thanks.

NZConvertible

Yep, I see no need to remove it with a stock turbo.

You're not getting 10psi without an FCD, fuel cut is at 8.6psi. There’s no way to stay down at 8psi without either porting the wastegate or going back to a restrictive exhaust. Restricting boost by restricting the intake and exhaust is completely counter-productive, but I guess it depends what the owner wants and is prepared to have done. FWIW, I currently have a full 2.5" exhaust, 3" TID, pod filter and a massively ported wastegate and see 8psi. My car is faster now than it was making the same boost with stock DP, stock TID and unported wastegate.

88rxn/a

iTrader: (6)

i thought stock boost was a little over 6psi. my manifold to turbo exhaust leak must really be killing my performance cause im only hitting around 6 with a ported wastegate with 2 1/2 inch DP to 3 inch catback with no cat.

Mr rx-7 tt

iTrader: (5)

I am getting up to 10 psi. The boost is going past 8.6 and it's bucking at 9.0 and 10 psi. (Gauge may be off).

The car is a daily driver and the owner isn't trying to make hp. The car is bone stock other than a dp. He has a third gen for his "speed fix" I guess.

NZConvertible

That's weird... I'd try to verify with another gauge if you can.

You shouldn't get that much extra boost just from a DP. You might want to check that the wastegate hose is secure and leak-free, and the flap opens when you put pressure to the hose.

nzs4

you say u need an upgrade fuel pump for 10psi? can u just upgrade the fuel pump and nothing else? is the problem that the injectors will give more fuel than is there, even with stock ecu?

13b4me

I'm gonna have to agree... Sounds like either a bad wastegate actuator, vaccum activation hose (the one from the fitting on the compressor housing to the wg actuator), or just a stuck wastegate... Is it consistant? Like the only way to avoid it is by staying @ < atmospheric?

NZConvertible

If you want to be completely safe then yes. 10psi on the stock fuel system is bolderline. An mild upgrade like an FD pump is cheap insurance.

Absolutely, plenty of people do it.

Not quite sure what you mean. The fuel pump is the weak link in the FC's fuel system. Even though the injectors can flow enough, the fuel pump can't provide enough pressure to them.

arghx

iTrader: (3)

holy crap you can get an FD pump or Warlbro 255 for < $100 and put it in in a an hour or less

hmm I wonder how much a rebuild costs...