CA18ET/DET hybrid build.

[CNHSS1]

the ET head is a very poor design imho. You will need to at least clean up the ports as the two halves of the casting leaves a step where the casting material flow joins. The ports are at 90deg to the valves, so really poor, so needs radiusing at least in my opinion. Bigger valves will only help if you do a decent amount of headwork, I know Shaun S13Eater did loads!!

without a cam regrind you will be having to use more boost to get each gain, so lowering efficiency. The std cam is restrictive over 5,3k-5,5k. A regrind will allow the power to not drop off till over 7k. The rocker shafts aren't really safe for use over 6,8k, above that they need to be removed, stud locked and ideally crossdrilled and grub screwed to stop them pulling out.

30psi on here modified a bottom crank pulley to suit the DET crank nose, reasonably easy for a machine shop.

std inlet manifold is restrictive too at the projected boost levels and flow volumes, ideally a front facing plenum or modify std one to front facing is needed

[Westerlund]

Thanks for the great input!

I will re-grind the cam then, and a friend of mind works on the cylinder heads on the local engine shop, but he only shimes the heads and grind valves no big experience with porting, but i will leave my head to him so he can clean up the ports a bit as he have tools for it.

I will see if i can get a CA20 intake for it with forward facing throttle body, i want my engine to have a stock look and no big custom intake.

I can consider to run a custom exhaust manifold but building a downmount manifold and wrap it with heat bandage so it's not that obvious that it's a custom manifold.

The silvia s12 is quite rare in Sweden, most of them have been taken by rust etc so not many swedes do anything constructive with them so there is wery little knowlege about the CA18ET engine when it comes to tuning beyond a t25 turbo and a Saab IC, so i am happy for every Good information i can get about this head/engine.

I have read the basic thread on the ca18et tuning on this forum (very good info) and a bit on s12.org, but often when someone wants to build on a ET head everybody starts asking why he dont use a DET head...
In-areas of giving some constructive feedback about the 8valver.

[s13eater]

my old spec, ported head, piper cam, top mount exhaust manifold with garrett t34 turbo, custom front facing plenum, 63mm throttle body, o ringed block, je forged pistons, 200sx rods, squirt jets, lightened flywheel, s13 clutch, 444cc injectors, custom billet fuel rail, walbro fuel pump from gtir, ajustable fuel regulator, omex 500 managment,3 inch exhaust, uprated evo intercooler, 3 inch pipework.

[Westerlund]

Originally Posted by s13eater

my old spec, ported head, piper cam, top mount exhaust manifold with garrett t34 turbo, custom front facing plenum, 63mm throttle body, o ringed block, je forged pistons, 200sx rods, squirt jets, lightened flywheel, s13 clutch, 444cc injectors, custom billet fuel rail, walbro fuel pump from gtir, ajustable fuel regulator, omex 500 managment,3 inch exhaust, uprated evo intercooler, 3 inch pipework.

How much did you get on the dyno with that spec?

[CNHSS1]

Originally Posted by Westerlund

I have read the basic thread on the ca18et tuning on this forum (very good info) and a bit on s12.org, but often when someone wants to build on a ET head everybody starts asking why he dont use a DET head...
In-areas of giving some constructive feedback about the 8valver.

to be honest, if its performance vs cost, dropping a DET in is the easiest and cheapest option. I ran the engines not in a silvia but an odd UK made car, which came with the ET in it from the factory and the hillclimb class rules at the time meant you had to use the original engine block type and head, hence putting all the effort to modify the 8valver (rules since changed).
S13Eater probably pushed the 8valve as far as anyone in terms of outright power, something like 305hp iirc. As mine was used for hillcilmbs and sprints I used a smaller turbo than Shauns, so mine made 282hp.

as they are essentially the same bottom end design, using DET rods and pistons or steel/forged versions is easy. The main changes made to the block was machining the oil galleries and fitting DET oil squirters to cool the underside of the piston crowns and a crank brace. I made a custom one at the time, but would just use a DET one now, fits easier and costs less.

the head is the main difference. The ET 8v design is average whereas the DET 16v design was really good for its day. As mentioned before, to get more power you need to free up the breathing about 5k, or all you end up doing is stfuffing loads of boost down it, which is inefficient and just bumps the air temps up really high.
some work on the port shapes and the cam will see it work happier to 7,2-7,5k rpm. Above that reliability could be an issue. Modify or at least stud lock the rocker posts. One of the guys I race with has a bigger valve ET head but to be honest to make real advantage of the bigger valves you need a bigger turbo and the small gain at the top end is offset by a loss of mid range imho.

I had some vernier pulleys made, to swing the autosprint and piper cam timings, but they only make a very small difference, and really only if you have a decent aftermarket ecu and mapper, more to perfect the timing really.

instead of a thicker metal headgasket as most DET guys use, I used MIG wired block, a std Nissan HG and machined the piston crowns to drop the C/R. If I did it again, I would just use a top quality DET metal HG (HKS or Greddy etc) and not bother machining the block or pistons. Don't go mad on reducing the CR imho, 8:1 is low enough and if using E85 you may be able to get 8.5:1 and not get knock. Keeping the CR helps spool and lowe to mid drivavbility imho