Papercup's V8 RX7

[anonymous-user]

Update and video clips please

[papercup]

'Ring trip. MPG:

1. on the way there, constant 80mph. 23mpg
2. on the 'ring, pushing hard. 11mpg
3. on the way back, constant 90mph. 22mpg

More to follow when i have time.

[Janosh]

So not much improvement in mpg over the rotor then!?

[ecowatt]

Just loved reading through the posts. Great topic!! I had an RX7 and had to change the motor after it went bang. I considered this route but opted to replace the engine with a standard unit from a breakers. If you had to do it all over again would you follow the same route?

My Rx7 gave me about 17mpg lol - awesome bit of kit.

[Ponk]

papercup said:

'Ring trip. MPG:

1. on the way there, constant 80mph. 23mpg
2. on the 'ring, pushing hard. 11mpg
3. on the way back, constant 90mph. 22mpg

More to follow when i have time.

That's really impressive considering the power. I imagine at a UK friendly 60-70 it's even better.

[papercup]

the rotary did under 4mpg on track......so did another friend's one running similar power.....so the V8 is way better!

[maximtaylor]

For the power its making, its very economical

And its comfy on long journeys, like coming back from Nurburgring today.

Thanks Andy

[Rawhide]

Nice work Andy... so did it break 8 minutes or was it too busy to set any quick laps? Did you have any overheating issues?

Hope to come for a ride sometime.

[slickchange]

Great stuff , glad your enjoying the new and improved road and track rex! I'd love to own a ls1 v8 rx7 someday. If you ever want to sell it look me up!

[papercup]

I should update this more often, I am falling behind.

OK, ring trip: the usual carnage on a tourist day, though worse than i remember it from 2006 when I last went a few times. They haven't made the car parks at the ring any bigger and the gridlock whenever the ring opens and shuts (due to brits crashing, generally) is ridiculous. They have however taken the cafe in the middle of the ring car parks and turned it into a 50s Yank-themed 'diner' which is pants. Really, WTF? The coolest race track in the world, with years and years of heritage and history and they copy sodding Happy Days?

Friday: Get there 4ish and ponce around a bit, visit where we will be staying (Frozenspeed Jochen's gaff, very nice and welcoming, top bloke). Get 3 laps in. It appears I have forgotten huge parts of the track, so take it easy. On road tyres anyway as I never intended to be in a huge hurry, this represents somewhat of a baptism-of-fire for the not-finished Rex, and the weather looks crap for the weekend anyway so 888s across Europe didnt seem clever.

Saturday: chucks it down all day. Do no laps. Sliding around in the wet and looking at all the crashed cars is bad enough, but you want £20 from me as well? Apparently Sunday will be fine, so happy to wait.

Sunday: Sunny, lovely weather. We are out first thing but its greasy as hell still on the higher parts of the track (middle and end) and under the trees. Wait a few hours. Go out when its fine and do 4 laps in a row, primarily because the queue to get back on the track is shorter than the one to leave the track and join the traffic jam outside, and my car is overheating. She runs too hot, like I thought. While on a motorway on the way she sat at 90c all the way, on the ring I am in more of a hurry and its 100-105. When i stop at the end of the lap its nearing 120 as I get back out. Not good. As I speed up during the day I can hold it at 110c. Slowing down to 60 for the start-finish straight before stopping gets it to 90, but when the track shuts and I am forced to sit in a queue I see the needle hit 123 before it stops moving completely. I go for a drive in the country to escape the carnage but when I get back its climbing while I look for a parking space. 9 laps in total today and not a single one is free from disruption as the crashes come thick and fast all day.

So....I was right. She's too hot. Time to get my bonnet back on and change the fan.

Edited by papercup on Wednesday 27th October 14:38

[papercup]

Other stuff: the gearbox overheats. It gets hot, smells (and gearbox oil has a certain smell, so its obvious) and doesn't want to change gear. Getting from 5th back to 4th (the two most commonly-used gears) when its hot almost needs two hands, and I miss 4th constantly, hitting what I think is the gate but is actually the gear itself and its too hot to engage.

I don't like it anyway. The ratios are all over the place. 1st is useless, I dont use it at all. 6th is so high its ridiculous. That would be fine if 1st-5th were usable, but they are too close together, especially for a car with this power-to-weight.

I meet a guy, while parked on the start/finish straight of the 'ring while waiting for it to be opened again after someone binning it, from www.gdcars.com who are from Nottingham way and build a replica of a Can-am-looking Lola T70 car with a 6.3 LS1 in it. He tells me of the Tremec Magnum, which is the new 'race/performance' version of the Tremec T56 which I have. Better shifting and stronger. Interesting. I may end up putting a small gearbox oil cooler and leccy pump on for the meantime, but I am looking into these seriously.....

There is another choice however; change the diff for something far lower, and put that cooler on it....that could fix it all, and cheaper than a new gearbox eh?

We'll see. No hurry.

[tinker-27]

higher ratio diff,

[gsd2000]

If you go for the magnum box get an uprated one from the states as in standard form they are less forgiving if you miss a shift, and more likely to break, but are alot smoother than an old t56.

Edited by gsd2000 on Sunday 31st October 09:50

[efiniste]

I'll be keeping an eye on what you come up with for a gearbox fix. I'm finding the exact same thing with mine. Awesome conversion and a monster of an engine, but the gearbox is a dog. Especially when you're used to the sweet shifting Mazda original.
Are you running a 3.9 diff? The only lower ratio options I've seen involve grafting a Cobra diff and drive shafts in. Do you know of any other options?

Steve

[redgriff500]

Just stumbled across this thread - a good read.

Any updates ?

If you knew at the start what you know now (specifically about the box) would you have done it differently / at all ?

[papercup]

OK, I've been remiss about updating this. Its cold out there and the last time I went to Craig's I couldnt feel my feet after a while. Been driving the car around a fair bit and washed it at the weekend so really must take some pics and update this a little. The temperature woes are over and done with, for instance, with the return of my lovely vented bonnet and the most powerful radiator fan available in the UK

I must also do what I said I would at the start, and have done so fitfully throughout the thread; proper cost breakdown for all aspects of it. I've wanted extras and they have cost, and other things I just had to do. My grand plan is a complete breakdown including optionals and true costs of things.

Would I do it again? Yes. Would I do anything differently, especially the gearbox? No, because I didnt know and had to experience it all to know better. I already knew it was the worst thing about the conversion, but what do you do? I'm a picky sod. I want perfection, which is hardly fair.

Actually, I would do one thing differently. The air-con pump was from a 99-model camaro (the 2006 original fouls something so you need the old one with the pipes coming out in a different place) and we really should have just had the damn thing rebuilt before we fitted it. After getting everything connected up and gassing it up it st itself immediately and leaked everywhere. Of course it did. Everything off and get it rebuilt and its been all back together since about November but I havent had it gassed up again as its bloody freezing and who cares? Still annoying though.

This is all hindsight though, as is the quickshioter on the box, which would have been far easier to fit with the box out of the car; but then I wouldnt have known I needed it and would always think 'I wonder if I did?'.

One thing; you will find me treating with utter contempt muppets who say things like 'throw a V8 in it, its simple, they cost tuppence'. I've seen how much work went into this and getting the engine to fit was the easiest and quickest part. When it comes time to connect the propshaft and program the ECU.....thats when people regret their hasty talk.

[RobCrezz]

Good to hear you are still pleased!

[4packet]

Have been waiting for an update on this thread as considering this conversion myself. The gearbox and associated ratios is perhaps (aside from the projected costs I've calculated) my main concern. What were the issues with the poor shifting/overheating originally and how have you overcome them? Do you know which ratios you have in your T56?

Do you think the Cobra diff is the way to go in the future or are you happy with your '5 speed'?

Thanks in advance

[papercup]

4packet said:

Have been waiting for an update on this thread as considering this conversion myself. The gearbox and associated ratios is perhaps (aside from the projected costs I've calculated) my main concern. What were the issues with the poor shifting/overheating originally and how have you overcome them? Do you know which ratios you have in your T56?

Do you think the Cobra diff is the way to go in the future or are you happy with your '5 speed'?

Thanks in advance

Rex is in a bodyshop having the front end finished off. The bumper wanted some work; after an off into the gravel at Lydden last year and 2 years of racing and trackdays it was just a bit of a mess. The old manky bonnet pins had been drilled out of the bonnet and needed filling, and the new sleek ones we'd fitted in the standard bonnet are going into a new position (behind the headlamps, not inboard of them) in this bonnet. New headlamp covers; the originals are known for snapping their mounts and mine had broken both sides. Making the bonnet fit with the V8 was never quite finished, so more is being shaved off the big vent holes in the middle and the grille is going back on (you could just reach in and undo the radiator header tank before!). Then new paint for the whole front end and one door (the last panel with its original paint, and it was looking very '15 years old' with touch-ins here and there and a few dents).

When its back, it needs to go back to Craig to have the air-con gassed up; we assume it will all work fine as the compressor was rebuilt months ago; it just got cold so i never bothered with it.

Gearbox; only overheated at the nurburgring, and due to standard bonnet and weedy radiator fan, the engine ran ridiculously hot as well, which must have contributed. So i must check that when i take it on a track in the UK that the gearbox still overheats; i don't know that it will. I will post up here when i trackday (which i will do first). We'll see. I will then do a sprint or two perhaps, which are too short to affect the 'box.

Gearbox ratios are:
2.970:1 (1st gear)
2.070:1 (2nd)
1.430:1 (3rd)
1.000:1 (4th)
0.840:1 (5th)
0.570:1 (6th)
which i got from here: http://www.kgbanswers.com/what-is-the-stock-gear-r...

I've looked into the Magnum, and different versions of it with higher 1st gears. You know what? On the road i don't care, i just drive my dog-leg 5 speed and i'm quite happy. Definitely put the quickshifter on it though. But the car is fine; I may change my mind next time i am on a track or at the 'ring, but as a road car its great.

I'd like to change the box just because I'd like a better one but I am not spending thousands on it yet. Cooling this one will be a pain; it has no cooler so will need one, and a pump.....whereas the Magnum is plumbed for it already. So I'll see how I get on. One thing is for sure; I am not going to spend loads this year as I have plenty of other toys and just bought a new sportsbike as well. I've been driving the car loads and as a daily driver, with its interior re-fitted and its nice stereo system, its great, and very entertaining to boot. Right now I am content.

The answer really is to change the diff; the fact is that the Rex diff is too low (or high?) and the gears simply want spacing out a bit. I just can't be bothered right now and will let someone else go through it all first. Once its established as a swap and Craig can knock them out in his sleep (like he does with fitting V8s) then I'll probably do it.

But I wouldn't let you put this off. The car is fantastic, and barking, and drivable, and entertaining, and.....its many things. I'm just going to use it this year, and slow down, and stop worrying about every little thing I can perhaps fix by throwing thousands at it. Ask me in 6 months.

But do it, you really should. Yes, the gearbox is the worst part, but its not that bad!

[4packet]

Thanks for your detailed response! Would be great to see some pics of it completed. The steering rack position vs bonnet modification is also something I'm weighing up. While it is possible to lower the engine sufficiently to clear stock bonnet it does involve bump steer corection on the steering arms which I don't like the idea of. I'm also struggling to find any mention online of the sump to road clearance. Are you happy with your ground clearance?

Martin