Firehawk's N2 racecar project

[andrecorreia]

it's fia aproved?

[firehawk]

Nope, not FIA-approved - hence the quite affordable price. If your class requires a FIA-approved fuel cell, go for ATL but be prepared to shell out at least four times as much cash.

[firehawk]

Ok, finally the engine is starting to run a bit like it's supposed to. Without ignition advance, it started and idled nicely but didn't really pick up revs at all. Now that the advance works, it both starts and runs properly.

I hacked together a quick'n'dirty method for gathering enough vacuum to provide the standard ECU a MAP-signal. As mentioned earlier, the ECU itself is modified slightly to overcome the lack of a TPS, air temp sensor and the idle mixture pot. These have no function on the ignition side of things so just faking them with two-resistor voltage dividers works quite well. The ECU does throw error code 11 when the diagnostic plug is connected but this is completely harmless as it only indicates that the idle switch was open on power up (the switch is normally inside the TPS).

Since the TRD intake manifold only provides vacuum ports from cylinders 1 and 4, I took those two, connected them with a Y-junction and ran a small hose via a filter to the MAP sensor. This seems to work reasonably well and the ECU runs the car with the stock ignition advance map. Since the fueling is performed by the carbs, the slight "jumpiness" of the vacuum doesn't matter as much as it would with ITBs+injectors.

Now that the ignition advance works properly and the engine starts to burn the fuel earlier, I found out that the carbs are way too lean. The engine idled very nicely, at a stable 850rpm but when carefully pressing the throttle, the carbs spat puffs of smoke and the exhaust popped and crackled loudly. On the other hand, the acceleration pumps seem to work exceptionally well with the 40 nozzles as a fast dab of the throttle picks up revs very sharply without a hint of hesitation.

A friend of mine shot this video while I tested the throttle response and tried to peek at the smoke-spitting carbs through the gap under the raised bonnet.

http://hanza.1g.fi/kuvat/sekalaista/corolla.AVI

Even with the muffler I added, the exhaust is ear-piercingly loud and on the video it's hard to tell when it backfires because the camera's mic gets completely swamped. Also, the recently applied heat-resistant paint on the muffler started to emit an acrid smell and white smoke towards the end of the video.

Anyway, since the engine ran so obviously lean, I pulled the 52.5 pilot jets and 135 main jets and skipped two sizes on both and replaced them with 60.0 and 150. No more backfire and the engine still revs quite eagerly. It may have gone a bit too far into the rich side but I won't know that for sure until I get to do some actual full-throttle driving. Gotta bleed those brakes first.

[Ivan141]

That sound! Very nice..I like!

[cavey]

jumalauta! now that is some engine noise

[firehawk]

Ok, I'm back. The CRX needed more of of my time than I had anticipated so there wasn't really much time left to work on the AE86 during the summer. However, now that the racing season is over for now, I can return back to working on my dear hachiroku.

I'm pretty much continuing from where I left the car in May so the first thing that needs to be done is mounting the fuel tank and finishing the fuel system by adding a swirl pot and pumps. Also, the wiring to the pumps needs to be redone since I just made a quick hack to get the engine running and there are no fuses whatsoever between the battery and the pumps.



Yes, the fuse panel is made from plywood. Although I'll probably replace it with carbon fiber once I know the final number of fuses I'm going to need.

To keep the fuel inside the fuel system and not leaking all over the car, I first needed proper fittings and hose. The TRD bible specifies that the N2 cars used AN/JIC -6 fittings so I figured out what I'd need and ordered them from Summit Racing. Their own brand of hose fittings is pretty good quality and a fair bit cheaper than similar Earl's or Aeroquip items. I also needed a fuel pump and a pressure regulator so I ordered a basic Carter pump and a Holley regulator at the same time.





I still needed a swirl pot and decided to build it myself so I bought some 75mm aluminium tube and 3mm aluminium sheet from a scrap yard and weldable AN -6 bungs from Summit. I cut the tube so that the volume of the pot would be around 0.7 liters and then proceeded to cut suitable pieces of the 3mm sheet to cap the tube. I used a flat piece for the bottom but forged the top cap using a few round discs cut from some MDF board left over from my garagemate's subwoofer project. I trust all my aluminum TIG welding to a local guy with a small workshop and he did some pretty fine work putting the pieces together.







The plumbing is now partially done but at least the feed pump still needs to be mounted. I'm trying to follow the Colin Chapman principle of making each part perform at least two different functions so the rear frame bracing doubles as the mount for the pumps. Also, the pump mounting brackets themselves act as guides for the fuel hoses and wiring.

[firehawk]

Ok, another day at the garage. Tried the video capturing capability of my new mobile phone and came to the conclusion that the image quality sucks.

[Eircamae86]

that is a thing of beauty,,,

speaking of Cams as Rossi mentioned, the biggest Ive seen/held were 14mm lift 16v 4age cams,, Im serious
There was also a titanium crank for the same engine, never was built (yet)

[firehawk]

Ok, like nzae86 said in his N2 racer project thread, sometimes you have to go backwards in order to go forward. I've been doing that a lot lately.



The reason for this is that I'm taking my car after easter to a workshop for building the rollcage and the guy recommended that I'd strip the body down to a bare rolling chassis to make more room for him to work. Also, he advised that if I want to use equal length links on the rear axle, now would be a good time to build the housings for them. Firstly - the cage is not yet in place to make things more difficult and secondly, he'd be able to brace the housings directly to the roll cage. For now, I only have one housing done and it's made of cardboard.

Also, through an amazing stroke of luck, I managed to find a pair of 13" Compomotive CX centers in 4x114,3 despite of them having been out of production for years! This means that I can forget hunting for 14" tyres and run 13" Formula 3 Dunlop slicks instead. A friend knows a guy from an F3 team and they regularily sell their slightly used tyres quite cheaply. Along with the centers, I got a pair of 4.5" outer and 3.5" inner rims, with bolts and O-rings for building two wheels. These will combine to a pair of 13x8.5" wheels with a ridiculously negative ET.

Now I'll need to refurb the front wheels because the previous owner had sandblasted them and painted them red. Getting them same kind of finish on the old outer half as on the new ones is not going to be fun, though..

[firehawk]

Ok, there's now two holes on the floor. I cut the top and the bottom of the original bracket but left the side for now so that I can put the axle back on until I've made the equal length arms.

The floor under the rear seat is made from very thin sheet, so I welded some strips of 0.8mm sheet on the edges of the holes for reinforcement.

My friend folded me the "blank" boxes for the housings from 2.0mm mild steel so they should be sturdy enough. These are straight U-profiles 510mm long, with 140mm tall sides and 51mm inner width (55mm outer). I copied the shape of my cardboard mockup to the sides of the boxes and will cut them into shape today.