Cutting gas tank, doing side exhaust, adding rear diffuser.
 

Well it's finally time. I'm tired of fuel starve so the gas tanks going to get cut in half. I'm going to have a local shop do it for about $150. It's not only the fuel starve issue though. The main reason I want it cut is to 1. Install a side exit exhaust out the side skirt in front of the rear tires so 2. I now can do a flat bottom and proper rear diffuser.

1. I'm going to have to figure out if I can reinstall the fuel gauge sensor.

2. How loud is it going to be because I wanted to do a fuel cell but the cost just sucks. So I won't be doing dual side exhausts at 2.5" but doing a single drivers side exit at 3" because the drivers side tanks getting the chop and not the passenger.

I guess wish me luck and comment with any concerns or ideas we might miss.

Sounds like a huge undertaking. Good luck bro! Keep us updated.

Single 3" side exit exhaust will be mega loud - maybe 105Db or higher on standard 30m drive-by test, even if you have room for mufflers.

Would be too loud for most race circuits down-under, let alone street.

If you are going to chop up tanks, and baulking at fuel cell prices, then I respectfully suggest you rethink your strategy.

If you are modifying your supply system to a return system, you can do a foam-filled tank (fabbed in ali) and 2-litre external fuel pot .. plumb a low-pressure lift pump from the foam filled tank to the pot and high pressure pump from pot to engine with return line to the main tank - that will solve the fuel starve issue.

If you are retaining the OEM fuel delivery system, your options would appear to be more limited (I assume you;ve already considered and baulked to the CJM fuel system)

There is benefit in keeping the fuel load inside the wheelbase, but even the Nismo RC race cars put the fuel cell in the spare wheel well which is the other option.

I'm interested in your fuel system design in any event - let us know your thinking ...

RB

Ok in less than 45min I unbolted the CBE from the X pipe, removed the W and Y braces, removed the crazy light carbon drive shaft, heat shields and disconnected the E brake. Moving nicely.

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I tested before as is and driving on the highway under normal 70mph db was almost 100. I think it was 95db. 80mph was like 98db. WOT windows up or down i was at 113db in the cab. I agree it might be louder. Behind the car i maxed the meter out at 130 with a 5k rev :). Normal driving though when its hot its not bad now! It could be a little louder :)

Why do all that if i dont need to? Cut the tank in half seems a lot cheaper at $150 no? My fabricator suggested fuel cell, external surge tank, return fuel system etc etc. keeping the fuel around the oem in-tank surge and everything OEM besides half a tank seems much easier too no? My fabricator is very worried about not doing an external surge though! He suggested it still no matter what i do but do 370's need it??? I meant id have to do the surge, pump, lines, new fuel rails etc etc $$$

We've look at everything placement wise and still need to corner balance and i did show him the RC rear fuel cell. He thinks low and forward is better even though ive told him im 58/42 weight ratio right now with 1/4 tank of fuel. Also my rear diff cooler and pump are in the way of that setup. We'd have to move it all. For corner balance my way isnt bad since im removing half the fuel from the side i sit on but it wont help front to rear weight. I just need to keep cost down.

I was thinking about noise outside the car ... which is what we need to manage to avoid citation by local EPA - my MY03 STi was pinged remotely by noise-police and I was required to revert to OEM zorst pending A$22K fine (I already had 2-strikes, re-installed OEM zorst - noise tested OK and re-installed 4" dump and 3" system twice an EPA knew it).

Not sure what regulations you need to comply with on the road or the track, but here, we are required to comply wit 75Dba @ 30 metres drive by under WOT for track day and 95Dba @ 30m on a race day.

Road regulations are 85Dba with noise meter microphone 1m fro exhaust outlet at 45 degrees and engine free rev'd to 65% of OEM redline at which time the test official side-steps off the throttle ... HFC are NFG as they cause a crackle which spikes the noise over the limit.

Anyway - good luck with your project .... I'll be fitting a 95-litre bladder tank to my car when the cage goes in.

Please take photographs of the tank inner structure if possible. I've been wondering about it since I got my car.

We don't really have noise police here. Just some get mad if it's to loud and will write a $100 ticket but nothing else. I used to live in a EPA county but not anymore. Hell Harley Davidson guys are louder than anything I can manage on the road! As for the track most are around 100db but I've never been told to stop. My zx6r was the loudest out there with a custom full exhaust I made and I never got yelled at and I know I was pushing 130+. Fingers crossed it all works out!

Thanks!

I will but there's lots out there already.

Ok the tank took about an hour alone. Pretty easy as its only held in by two straps and 3 hoses but the two 17mm strap bolts have zero room to remove from below which are above the subframe. I had to take two nuts and from inside the car, lock them together around the threads sticking up from underneath and then loosen them. Then below I could remove with my fingers holding the tank up with my other arm.

So much room! My heads spinning with all the activities we can do! So many activities!!!!

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Whole body can fit!

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Onto the cbe. Here's where it will go. After I finish cutting the hole we'll weld a box around there of mild steel to re-enforce what came out. As you can see through the egg shape hole there's about a 4x3" hole already in the middle of the frame the exhaust will pass through nicely. Then we just have to cut a hole in the side skirt and one more behind the side skirt in the quarter panel. Now to figure out if I'm going to buy a Y pipe or make one...

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Interesting and I hope it all turns out well. I am just thinking with half a tank you'll be filling up very often. I'd think a surge tank setup would be effective in handling fuel starve with the stock tank. I didn't go for one just because there's no real place to hide it and wanted to stick with a clean interior, I don't think you have that issue. Also with 95-113db inside I'd be less worried about tickets and more worried about ear protection.

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Tracy Ramsey

The surge tank was 100% on my mind but after buying a tank, lines, fittings, fuel rails, CJ's return setup, external or internal pump etc etc I'd of been over the price of CJ's in tank fuel starve fix. Who knows, maybe this still won't work, however Chris Forsburg runs a cut tank, not sure about a surge though. All I know at this point is that this is easy and gives me my other 2 wants! (The new cbe and flat bottom with diffuser). As for filling up you're correct. But I've owned dodge trucks and jeep wranglers, I've been used to 200 miles on a tank. My car gets about 24mpg street driving so I'm guessing I'll keep about 10 gallons, so 240 miles will be fine. On the track i guess maybe 8mpg or 38 laps at Mid Ohio which is more than enough for a 20 min session.

Your way is definitely much more cost effective. Going easy on the track got me 8.4, harder was getting something around 6-7. Depends alot on the track/driver =P and I know I'm not that good.