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I manged to produce a custom pulley based on autocad drawings that I made. Only issue I still have is with fueling. For some reason the Walbro 485 doesn't work under boost in the stock fuel basket. My fuel pressure drops when I start to get boost.
So at the moment I'm waiting for CJM to finish their new double pump assembly and hopefully that will solve all the issues.
I manged to produce a custom pulley based on autocad drawings that I made. Only issue I still have is with fueling. For some reason the Walbro 485 doesn't work under boost in the stock fuel basket. My fuel pressure drops when I start to get boost.
So at the moment I'm waiting for CJM to finish their new double pump assembly and hopefully that will solve all the issues.
How old is the 485? I had a similar issue, my 485would drop pressure under boost. But it had worked for a long time prior. I swapped in a new 485 and the problem went away. I assumed the pump was just going bad. I've since switched to the CJM twin pumps. However, thatv35guy still has a walbro 485 in a stock fuel basket working fine on his setup.
That's interesting. The pump is new but it could be damaged since it was running a bit dry before I made some modifications to the pick up filter.
It will be winter here soon so I won't be driving the Z for five months or so. During the winter I will switch for the CJM dual pump system or Radium system that is under development.
There is no going back to fuel. I have already invested in the ID1050x injectors, flex fuel sensor, ethnol proof fuel lines and bigger fuel pumps that I would't have needed with fuel. E85 availability is good here and it's cheap. Dyno numbers with E85 are good too and it's a hassle free solution.
Just started a project similar to yours for SCCA National Time Trials. Engine mod.s are very similar and I'm now at the decision point of SC/turbo boost options. I like the SC for track use but not the tuning limitations. Mind telling what your boost pressure target is?
My Hp target is around 500. It's winter here and the car is now stored. I'm still waiting on the CJM fuel pump setup. If it doesn't come soon I have to look for other options.So no dynoresults yet, sorry.
I can't remember how many psi is the capability of hks8555. You can find the compressor map here.
I track my car and really like the linear power output of the SC. For a track car I would go with a more aggressive cam. My car hasn't seen much tracktime since I went SC. I've have had lots of issues and very limited time to work on the car. Now I got a new house with a garage and a new job so hopefully I have more time for this project.
One thing to keep in mind is that FI generates a lot more heat. Even more so with a turbo setup. For this reason and the linear power curve I wen't SC for my weekend/track car.
Originally Posted by Steve Parsons
Just started a project similar to yours for SCCA National Time Trials. Engine mod.s are very similar and I'm now at the decision point of SC/turbo boost options. I like the SC for track use but not the tuning limitations. Mind telling what your boost pressure target is?
Thanks for the response although I asked the wrong question. Should have asked for your target SC rpm. And, appreciate the camshaft comment. Will work with Clark @ JWT.
The recommended rpm for the supercharger is 100 000 rpm. I confirmed this from the manufacturer.
If I remember correctly the supercharger spins 100k when engine revs are little over 7k. I can't remember exactly. I had to make the custom pulley so I wouldn't overspin with the ATI damper.
Ok. It hasn't been easy, but now I finally got some initial dyno numbers. From flywheel 530 hp and 580 Nm of torque. Little less that I expected but the car is a blast to drive now!
For some reason I still had issues with fuel pressure dropping at boost. We managed to keep the lambda values in check, but the fuel setup still has some flaws. During winter I will probably put new fuel rails and a bigger input hose.
The FPR couldn't drop pressure under 55 psi. Maybe it's because the surge tank gets fuel from 340lph intank pump and from the return of the two 250il pumps.Ethanol temps raised up to 65 degrees (celsius) which isn't ideal either.
Overall I'm really happy with how the car feels. It feels faster than my brothers 997.2 gt3 (on a straight line). I don't know if it is but fast enough for me anyway.
I bought a 280z and because of that this project car will get less attention. However I will iron out the imperfections and have it retuned after I have fixed the fuel issues.
If there is interest I can post some additional videos.
Here is a short clip from dyno. Not the final pull, but close to it.
If fuel pressure is dropping on pulls I speculate your pump is undersized. My DW320 pump started dropping pressure around 550hp. The options were to further increase injector open-time or go with a bigger pump.
Conway had a similar issue of the fuel pressure and he fixed it by increasing the size of the return side nozzle diameter. I'll let him chime in.
The 340lph pump is just the lift pump. The Deatchwerks surge tank has twin 250lph pumps that should be good for over 800hp. But I still have drilled stock rails with an6 lines. That might be part of the reason.
Basically it has a quantum lift pump that provides fuel to 2.5 Deatchwerks surge tank that has two 250il pumps.
There should be no doubt that the 250+250 couldn't provide enough fuel if there are no other restrictions.
I have a CJM stage 0 fuel return system and Aeroflow fuel pressure regulator. I have the oem rails. With the input side drilled open.
The surge tank has three inputs. Input from the lift pump, overflow back to main tank and fuel return from the engine.
Part of the issue was that the lift pump was just a regular in-tank pump. This created 20psi of pressure in the surge thank that affected the fuel return.
Unfortunately the pressure broke one of welds in the tank. I decided to go for a new surge tank, low pressure lift pump and AEM 400 lph E85 pump. In theory AEM pump should handle my 530 hp by itself. This would reduce the amount of fuel being pumped and it will make the fuel lines more simple.
I'm waiting for a few fittings to arrive to finish the new surge tank setup.
It's been a long time since I've updated...
Good news and bad news...
I redid all the fuel lines with AN8 and used CJM fuel rails. I also installed a Aeromotive fuel pump speed controller to keep the ethanol temps down. These changes solved all my fueling issues.
I also had problems with the car overheating. One of the issues was that I had deleted the bypass hose in front of the engine. Despite the general knowledge on this forum I didn't get enough hot coolant to my thermostat for it to fully open. After reinstalling the bypass-hose my coolant temps dropped as much as 10-15 degrees.
The biggest now is that I broke my second HKS supercharger. First one was the 7040 that I broke during a pulley change. I got the wrong advise from HKS regarding the pulley bolt thread direction. The second GTS8555 unit failed right after a startup and I had only done about 1000 miles of street driving. From the looks of it the O-ring failed for some reason. Due to the age of the unit (3 years) it's no longer under warranty. So I decided to open it up myself and see if it can be fixed. For some reason I couldn't get the impeller off the shaft. So it looks like that's that.
Now the easiest solution would be to get another GTS8555 (maybe). But since I'm really unsatisfied with HKS and tired of buying traction fluid worth of 400$ (in my country) so I started to consider changing the supercharger to a Rotrex unit.
By looking at the spec sheets it looks like the c38-91 would be an easy almost bolt on solution. However the CFM difference is so small that it would only probably bring extra 50 hp so I don't think it's worth the effort.
The "new" c38r-112 would be a great choice if I could only make it fit. It's 28 mm longer and the outlet size is 83 mm compared to 70 mm in the 8555. This would mean that I would need some sort of adapter to make it fit the HKS piping. This would further increase the length of the total package. So I'm unsure if I can actually make it fit. I thing next step is to bolt the 8555 back in and see how much clearance there is. One thing to note is that the drive ratios are also different. The 8555 has a 1:9.368 ratio and the C38R-112 has a 1:6 ratio. Also the max RPM are a bit different, 8555 (100k) and c38r-112 (90k).I think this can be solved easily by changing to a smaller SC pulley and using the original drive pulley from the HKS kit instead of the custom made 1:1 pulley. The biggest issue is however the the physical size and altering the HKS bracket/piping to fit the bigger c38R-112.
Thats no good ... sorry to hear about the troubles.
I deleted the bypass hose (along with every other unnecessary coolant hose) and put a 5mm hole in my thermostat plate that allows 'some' coolant to flow this also make bleeding my coolant system very easy.
I havent seen much information on the Rotex in these parts but have you considered going turbo? It seems like you're jumping through a bunch of hoops to make the Rotex work. I know many people start with superchargers and migrate towards turbos - just a thought.
10-06-2018, 11:03 PM
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