Hey guys, I finally got tuned yesterday and it turned out fairly well. The first tune was at about 8psi and I got around 265 whp and 195 ft lbs of torque. I was happy with that. My set up is in my sig, but it is basically a Greddy turbo, berk hi flow Cat, stock exhaust, and tru boost and UEGO gauges. I was hoping for 280 to 290 whp and 220 ft lbs. I knew the stock exhaust would keep me from hitting 300, but I want to get an HKS hi power or Invidia V4 (something quit) to get to 300 next year. Anyway, at 8psi and 265 I thought I would get roughly 20 more whp if I went to ten. Once my tuner got the a/f and timing where he wanted he told me to turn the boost up where I wanted it. As you know, the tru boost is a guess as to the exact setting you need to get a certain boost. I set the spring setting at 3 and the duty cycle to 30 the first time I turned it up and it went to about 9.25 and I hit 274 whp and 207 ft lbs. I said, I am getting close to my goals, another .5 psi and I should be close to 280 and 210. So I turned the boost up more but it started going lean (close to 12.8-13) in the area of 7000 rpms, and the hp outputs started going up and down after that 7000 rpm area. So he tried and tried to get more fuel in that area, but the a/f would only come down to about 12.5 after three more pulls. My last pull at almost exactly 10 peak psi was 264 whp and 191 ft lbs. !! The boost did drop off after 6-7k rpms, but I just thought that was the stock exhaust choking the flow or the tru boost being the tru boost and not holding right. After talking with Mark and a friend who came by to look at it, they said it could be the Wallbro 255 pump.

Supposedly, some of the newer Wallbros (made within the last year) have been known to have problems and can only push 60 psi of pressure. The tuner thought our stock pressure is around 50 psi and when we upped the boost to 10 psi it could have been maxing out the wallbro if it only was able to push 60 psi. That could explain why it was still going lean no matter how much fuel he added. The injectors were at 62% duty and he upped it to 70% duty in that area and it barely made a difference. We think it made it worse, because it left the injectors open longer and was just getting less fuel.

Okay, sorry for the long explanation, but I wanted to explain everything to you guys. The car ran like a champ on the way home. Definately better than the base, but it is not what it could be. I turned the boost back down to about 9psi to be safe and a/f were 10 going up to 11.5 up to about 6k rpms. My tuner had a big fuel pressure reading kit, but nothing fit the stud on the fuel pulsation dampener. He is going to find something to fit it this week so we can check the fuel pressure.

So, what does it sound like to you guys? Have you heard of Wallbros going bad or not being able to pump more than 60 psi? I don't think the exhaust would have anything to do with the fuel problem? Do you think 10 is too rich at WOT at about 3-4K rpms?

Any suggestions would be appreciated, so I can run it by the tuner.

By the way, the tuner is Mark at Turbo Tune in Greensboro NC, and he has tuned several S2000's with Greddy kits and with bigger turbos and SC's. The last Greddy S2000 he tuned (had a test pipe and 3" exhaust) made 307 whp. So I think he knows what he is doing. Thanks guys!

Rich

 

The Wahlbro 255 has been used to pump enough fuel for MUCH more than 300 hp. But you do need to get the fuel pressure checked. Adjustable FPR output should be about 45 psig at base, and climb 1 psig for every 1 psig boost.

As with any centrifugal pump, an increase in discharge pressure will cause a drop in flowrate. At some point, the pump will not keep up. You should be nowhere near that point at <300 hp, unless your fuel pressure is jacked up incredibly high, which would cause a terrible idle.

I don't believe your problem is running out of fuel. If you or your tuner have a scan tool / software package, you could read/log fuel pressure and injector duty cycle to verify that injectors are large enough to prevent feul starvation. Keep duty cycle from getting above 85%. Do you have stock fuel injectors?

And all else being equal, a restrictive exhaust will raise boost pressure (actually it raises pressure everywhere in the system). Sounds like you're losing boost though. I have no experience with Greddy's kit, but if you are losing boost pressure above 7000 rpm, I would check for boost leaks at the couplings first and then at the wastegate.

 

Thanks snake. I know that Wahlbro 255s are used for much high HP applications. Have you heard anything about some of them only able to put 60 psi out, or problems in general with the newer 255s?

The boost does go up to 10 if I want it to, but it want hold that boost. That may be normal for the Greddy to not be able to keep the boost up in the high RPMs, but I don't know. Could the stock exhaust be keeping the boost down? Just looking for ideas.

 

I edited the post to add more info. I don't believe the Greddy kit is designed for 10 psig boost. You may have to change the spring in the wastegate or add a boost pressure controller to get that much boost pressure.

 

The Greddy's typically reach the top end of there efficiency range at 10 psi from what I have read. Most people loose power above 10 psi with the stock Greddy. The kit comes with 550cc injectors and they are at roughly 62% duty cycle throughout the RPM range until 7000 and car starts to lean out. Boost leak wouldn't cause that would it?

I have a boost controller (the AEM tru boost gauge/controler combo).

I will see once the fuel pressure gets checked, if Mark has a way to check for boost leaks. I am sure he does. He is monitoring injector duty cycle through the emanage, but he said it couldn't monitor fuel pressure. I will ask him if he can log the fuel pressure by plugging into the OBDII plug.

So you did say that the stock fuel pressure is 45 psi right...

 

Yes at idle.

I don't know allot about Turbos but I do know a little about fuel pressure, injector duty and boost numbers. Your situation seems a little confusing to me also. I have a CTSC kit running 8psi at aprox 325whp at 12.1 afr with stock 360cc injectors. I'm running 95psi plus at peak boost from the fpr, so it is not ideal but it works reliably every day for me. I am still using the stock ecu. I will be getting 440cc injector at some point so I can drop the fuel pressure down to more safe nominal levels, though tecnically I should be able to run 9psi at that point safely. I will see where my fuel pressure and afr's rest with the 440's first before extending my boost any further. By the way I will be running the 440cc with the stock ecu as I can tune with regulating fuel pressure and my VAFC2. Big and reliable power on a budget is what I call this I don't think this kind of set up would translate as reliably to a turbo set up, but just thought I would throw a little contrast in here and see if it brought any light to your situation.

I did have problems with a new Walborro 255 pump not delivering enough fuel, so I replaced it with a used pump from another member that had a succesful CTSC set up, It was not a Walboro but something else that came with the CT kit years ago back in the early days. I have heard that there has been some bad 255's going around letely, but I don't know if that is just hearsay or true, it did seem to be true for me.

 

I was hoping that Mark was wrong on that, but it seems like you are the first I have actually talked to that had problems with the Wahlbro 255 He said that he could get it to flow a lot better by taking it out and pressing in the pressure relief valve 60/1000th of an inch. That will allow it to build proper pressure before coming out of the relief valve. He's done it to 50+ 255's. I just don't want to have to pull the stupid thing out again, although everyone says it is easier the second time around.

 

use the stock fpr! i have tuned many, many s2000 and always gone back to the stock fpr - it's rising rate works perfect.

now the walbro - i have seen a couple differnt versions of the 255 - i have learned that only use the ones that when you look into the output you see metal gears/bearings - the other ones were plastic and did not perform well - so check you pump b4 you put it in.

 

I'm using the stock FPR. The only thing I changed in the fuel system is the fuel pump and the injectors to 550cc. I even used the old sock off my old fuel pump, so it wouldn't interfere with the fuel level arm. It was still in good shape.

I already put the pump in, so can't check it unless I pull it back out to see if it has metal gears. Where do I look to check this?

 

I know nothing of the fuel pump issue but your number seem reasonable. I would lean to the V4 over the HKS due to size although it is untested with this turbo. I am sure you know this but as the car gets hotter it loses power. So more dyno pulls less power, it happens at the track also.