PaulFitzwarryne

Like many I have thought of installing a 12at engine. The frequent quote for its output is 160-165hp.

This is a great improvement on the 12a 100hp, and the 13b of 136hp, and looks worthwhile when considering the 13bt at 180hp is a more complex change.

The 60% increase looks impressive considering there is no intercooler, the ports are small. the header/exhaust is limiting, and the EFI is primitive.

After some research. I think the 160 hp comparison may not be accurate. One of the books gives the Jspec data as 130hp[JIS] for the 12a and 160hp[JIS] for the 12at.
UK data has 130 din for the 12a and 160 din for the Elford turbo which was a slightly better engine than the Jpec 12at. As a matter of interest, going EFI on the Elford added 5hp.

If the 160 was really JIS, then the hp would be in the order of 130. This is a 30% increase from 12a to 12at, equal to the 30% increse in going from 13b to 13bt

Thus, the Jspec 12at might not be a good choice when compared with going down the 13bt route. The 12at output can be reached much more cheaply with a header and modified Mikki carb.

Any comment appreciated.

S2-13BT

Another ACT fella huh?

The potential from the 13BT is higher but a 12AT is different. I suppose it depends on what power you want at the end and how much your willing to spend.

Of course you could use a 12AT engine with a 13BT turbo, to flow more air more efficiently thus giving higher output. Again, not as much as a 13BT with comparable mods though.

IMO the 13BT is the better option in the long run.

See ya
Christian

PaulFitzwarryne

When I was considering increasing power my thought was to keep to stock 12a as far as possible.

I agree 13bt has more potential but the typically quoted figures for the 12at were 160hp stock, 180+ with a intercooler, 220hp with increased boost. For a daily driver I was happy within this range, but I have some concern over whether they are accurate. With the current header/exhaust and carb mods , actual output of my engine is around 140-145hp. I would prefer about 180 for acceleration, easy driving and fuel economy.

Thus, my options in order of preference are:-
12at with intercooler on 6lb boost;
12a with porting; or
13bt possibly a series 5.
Actual costs are all in the $aus 4-5,000 range so that is not a concern.

My question is whether the 12at data is accurate, if not the 13bt looks more attractive except for the hike in insurance.

WackyRotary

I think 13BT is better for several reasons, one of which is more displacement! With more displacement comes more torque. 12a's of any form will have less torque then a equivical 13b with the same setup. OFcourse the acuracy of that statement is hazy. But a 20b or 4rotor engine will certainly have much more usable/drivable torque due to the extra displacement without the expence of bridgeports or other hp increasing techiques. Displacement is everything if you think about it. Thats why you don't have to modify a 20b to get it very fun. Ofcourse it is more fun when you can get extra boost and intercool it over stock and port it and haltech it.

Anyway, thats why I'd go 13bT before I'd go to 12aT. But if someone offered me a cheap 12aT, I'd get it ofcourse.

PaulFitzwarryne

The figure I have for torque of a 12at is 166lbsft at 4,000rpm which is quite an increase on the 12a of 105, and not too different from the early 13bt.

The data I have on an intercooled 12at is that it is the same as the 13bt What I am trying to do is copy a Jspec. The cost of the exercise will be marginally more than a 13bt due to the cost of a front mounted intercooler.

Why is the Jspec 12at so good considering its early design and limited components?

Adsy01

the 12aT are heavily over-engineered and that is the stongest point..

i had one in my S2 it was a great engine once boosted check it out on my website (link below)

MikeLMR

Japanese power figures always tend to be on the high side for some reason.

One of the performance guys where i work ( we build industrial gas turbines) said that companies often test their cars at higher altitudes and then correct them to DIN or ISO standards ( pressure temperature etc.) therefor you can fudge numbers and boost the H.P output to sell cars.

P.S where did you find out that Elford turbos had injection as an option ?

PaulFitzwarryne

Adsy01 you have a good site and linkages. Some of them look good for future reference when i decide which way to go. I wish I had a set of RXs to try each option.

Defprun

I simplify my life by keeping stock engine. Whatever my car came with is what im going to modify. I will rebuild it, but if it blows up..than i may do a change. But I stick with 12a. I like carbies. If you go 13bt, yank the efi install a nikki carby and go blow-thru turbo setup.

NZConvertible

My last car was a 1984 Cosmo with the 12A Turbo. I bought it completely stock and had it dyno’d soon after. With a clogged cat, it was good for ~135hp. I completely added a free flow intake (filter to turbo) with cold air supply, a complete 3” exhaust, removed all the emission gear and did a few more little bits and pieces. This combo produced ~205hp @ 8psi. The turbo blew so I rebuilt it and added a Series 4 compressor housing and wheel, which was good for about another 10-15hp and 2psi boost. I never got around to intercooling it, but a mate with exactly the same modes to his factory Series 3 Turbo (also 12AT) did add an IC made from two S4 core’s welded together. His made ~240hp, which was the absolute limit for the stock EFI.
The 12AT is a great little engine; they just seem to handle a lot more abuse than the 13BT and are obviously a lot easier to fit into a first Gen. But I’d stay away from the stock EFI; it’s very crude (analogue, not digital) and can’t control the ignition. My mate above has since added the entire induction and EFI system from an S5. The intake manifold required an adaptor plate, and the exhaust manifold is a custom tubular one. I can’t remember the power figure (it was heaps!) but it was enough for a 12.4sec quarter on stock 14” wheels and street rubber. It’s since received a T04 compressor section and Microtech EFI.

Adsy01

thanks Paul. I wish I had a set of Rx's too!! I only have the Red s3.... and ive only ever had one at a time

12months after selling my s2 (12aT) I bought the s1 as a daily driver and to have a bit of fun in.. it blew up and I had a chance to trade it for the s3, so I did

PaulFitzwarryne

MikeLMR my souce was Brian Long's book on the RX-7 at pages 57-68 on thr Elford turbo.

"With electronic fuel-injection, the offical power output was being quotedas 165hp at 6500rpm, while maximum torque had increased to 166ibft, at the same time the pice had increased to 12,000 [pounds sterling].' the top speed was given as 135mph, 216kph.

I think this was 1983-84. My Brother had the SU version while I had a Lotus Elan SE and 47. I also had a turbo 46 using twin 45s built in 1979, massive top speed but no power under 40mph in first!

lincoln must now have gone hi-tech, at one stage they produced the world's best road going steam engines.

PaulFitzwarryne

NZConvertible. Thanks for the info. The 12at seems to be a well designed and built motor, and I agree the EFI needs updating. I presume the data is rwhp.

I am designing my specs for the project. The only delay is the present 12a will not wear out. It's done 125,000km practically all long trips. I just put the top down and go. Like you I prefer a convertible, in this case a 1984.

MikeLMR

Hi Paul,
Have you got an ISBN number for that book ? I'm looking at buying an elford turbo in the future and want to learn some more about them first.

Yep, lincoln went high tech in the 70's and I work in the same factory that built some of those steam engines: D !!!! (elbeit under a different name)

Appart from electronics (marconi) has turbines pretty much dominate lincolns industry !

P.S did you see the elford turbo broshure I posted I while back

PaulFitzwarryne

MikeLMR The info you requested is:-

"RX-7 Mazda's Rotary Engine Sportscar" by Brian Long published by Veloce Publishing at 29.99 UK.

ISBN 1-901295-93-1
UPC 36847-00193-3

website: www.veloce.co.uk
e-mail: info@veloce.co.uk
fax: 01305 268864
address: 33 Trinity Street, Dorchester DT1 1TT

The book was published in the UK in 2001, so you should be easily get a copy. It's a great book as it covers UK, European and Japanese models.

Of interest is the notes on both the TWR and Motospeed turbo conversions.

I have never seen the latter which was a Weber carb/RotoMaster turbo system. It produced 200hp giving 0-60 in 6.2 seconds with a top speed of 145mph (232 kph)

Missed your earlier post on the Elford brochure so will look it up.

PaulFitzwarryne

MikeLMR, looked up your posts and found the brochure.
For some reason it did not come up under search.

The strangest vehicle to come out of Lincoln was a steam driven armoured road train used in 1899 during the South African War. I have no reference for its road test!

MikeLMR

Hi,
Paul I think i posted the brochure under a silly title like "thought you mighte like this ..." or somthing like that (yes I have taken heed of the post titles post )

Thanks for the Info on the book , looks like that one will be finding a place on my bookshelf in the near future

By far the strangest thing to come out of Lincoln during the second world war was a steam powered trench digging "worm" it could dig a huge trench in minutes while the crew where totally safe inside its armoured hull! ... it never saw service though

The 1st tank came from Lincoln also ... a development of a protoytype steam tractor !!

PaulFitzwarryne

MikeLMR. Obviously you know your factory history. The Number 1 Lincoln Machine was the first real tank and was tested up Cross-o-Cliffe hill in Septembe 1915. I did not know about the WW2 trenchdigger, only the Foster-Daimler trench crosser and Foster 'Big Wheel' which were weird early attempts.

I found the Elford brochure by going through your posts, if all else fails read the instruction manual. Peejay on another thread said he had a road test of from the Autocar. If interested you could possible track it down as most magazines will supply photocopies of past articles. I am not certain if your local library has back copies from 20 years ago.