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touge's ae101 racecar - ‘fab it all from scratch’ project


Rhyscar

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18 hours ago, shrike said:

No plans to convert to electric power steering? Ie from a newer corolla, echo , vitz, prius or GT86/BRZ?

Yes but no for a few reasons. I've gone with a MR2 electric PS pump because they've proven to be very reliable in different racecar applications. 

On-the-column electric powersteer units are good, but are tricky to get feeling right and typically involve welding/replacing the steering column (difficult to get road legal). On the AP4 rally cars they use a Woodward column and mount and have some technical document with LVVTA on how they get them through the cert process.

I pretty much wanted to avoid this level of complexity so have stuck with a tried and trusted electric-hydraulic system. 

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Thanks to @Guypie for machining my intake manifold on a 7deg angle. This netted me 16mm of additional bonnet clearance so I'm happy. 

 

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This should be enough to design some funky-shaped trumpets to fit under the bonnet. Very interesting seeing @kpr testing results, it seems shape doesn't matter too much, as long as length is correct. IIRC 130-160mm trumpet (330-360mm total) is what I was aiming for. 

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Lots of wiring progress lately. A bit more on that soon, but for now here's some satisfying pictures of general tidyness/not being hory. 

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Made a sweet bracket for the speedo sensor pickup off rear hub. This will drive the Monit (for wof purposes), but also allows ECU to do some launch/traction control things (compare front vs rear wheel speed etc)

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Sweet bracket for clutch and brake pedal switches. Included clutch to do launch control/flat shift at some stage. Lots of holes because aluminum isn't lightweight enough I guess? 

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Not much progress to report but lots of technical stuff going on with the design/fab of my headers, so sorry but this will be a nerdy post.. not claiming to be an expert, just figuring out how to make stuff work.. 

 

So here's my scratching for re-checking my length. Unfortunately I need to run 4-2-1 header as I can't fit 4x runners under the steering rack. The expansion chamber clashes with the swaybar (wasn't in the car when I mounted it argh!), meaning I've needed to push it back another 100mm. I'll need to incorporate the slip joins into the '2' section (because bottom section will be permanently attached to exp. chamber) as this is the easiest place to get the runners parallel where they'll slow into place.. This means my 9" secondaries are going to look more like 12", which by keeping overall length the same, will mean my primaries are getting close to 15-16" (which is the minimum as I understand it). In summary its complicated..... 

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With restrictions in tube sizes available (above calcs is inches ID), I've had to go for 44OD primaries (works out well as is the same size as exhaust port) and 57OD secondaries. Secondaries in particular will be a little larger than optimum considering it's only a 30" long pipe, so it will likely favour higher RPM's. As long its making solid power from 5-6krpm I'll be happy. 2zz's have a massive torque hole at 4krpm so I'll be bringing the high cam in as soon as possible. Might also push me to add a big cam sooner rather than later.. 

 

Found this super interesting paper on the development of the 2zzge. Pretty much says they designed this awesome high-revving engine and then proceeded to put a terrible exhaust manifold on it to reduce noise emissions and wasted all the hard work they put into the head etc. https://www.lotustalk.com/attachments/toyota2zz-ge-technical-data-pdf.1297134/

 

For the header design, I'm following the theory laid out in Graham Bell's Four stroke performance tuning book. Main examples are based on 2L touring car engines, which is pretty comparable to what I'm doing (12:1 comp, itbs & 9000rpm). All my sizing/calcs are firmly in what he defines as purely 'racecar' realm... I also think engine & ecu technology has moved on since early 00's which has proven you can get away with a lot bigger tubes than the 'old' rules of thumb. 

I'm using an adaption of a venturi collector design with a centre divider plate. Apparently the venturi and divider plate should be equal-sided triangle 1/2" bigger than the primary tube. Nailed the fabrication on the secondaries in particular which I'm proud of. Will be interesting to see if these work as it does essentially create 2x venturi effects in the same collector - 1 where the pipes join, then a second as it expands to secondary. Who knows if this will work as intended? 

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So this is my crossmember conundrum... I ended up needing a small bend between the collector and expansion chamber which is another compromise.. 

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Primaries are roughed-out in Kinex blocks. These are a bit of a spaghetti junction as the 2-3 cylinder runners need to go the furthest so need to take the 'under' route.

No doubt these will be refined a few more times as I confirm the position of the secondaries. I plan on tacking secondaries up to slip join, then start back at the top and work my way down. Wish me luck!!

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All this learning has taught me is everything is a small compromise when it won't fit in the car. Exactly how the power band will work out is yet to be seen, I won't be surprised if I end up making a few variations as I test these.. just got to keep putting in the effort and one day this damn car will be finished!

 

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