CA18ET/DET hybrid build.

[Westerlund]

First of all, english is not my first language so im sorry for my bad grammar/spelling.

A couple of months ago i bought a 88 s12 hatch with the CA18ET engine in.
I have decided to build a new engine for it and have starting to prep a DET block that i was going to put the ET head on to keep the old school look and the MOT guys happy.

The setup i was planing to run is:

Bottom:

*CA18det block
*Stock DET pistons and rods
*New oem DET oil pump
*Stock DET fly wheel machined for a Sachs 618 plate.
*New bearings

Head:

*CA18ET head
*Cometic MLS head gasket
*ARP head studs
*Maybe re-grind the stock cam
*Stock manifold (will port it)
*Stock intake

Air/and fuel:

*z32 MAF
*444cc GTR injectors with modified rail.
*Stock s14 turbo gt2860
*300x600 greddy IC
*AEM A/IC piggyback
*Blitz boost controler
*2.5" or 3" custom exhaust


The problems/questions so far i have read or noticed are:

The ET head head studs are 10mm and the DET are 11mm so i will need to drill the holes in the head a bit.

The DET crank is a larger diameter were the timing belt gear sits, have any one machined the ET timing gear to fit it on the DET crank or how did you solve that issue?

Does anyone have any experience of the AEM piggy back? I want to use that beacuse the ability to adjust the ignition to, not just the fuel.
The car will run on E85 so adjusting the ignition is a must to be able to get full advantage of the better fuel.
I've read that some people had problems with the AEM om newer cars like the Lexus GS300 that the stock computer did now want to cope with the AEM, so i was thinking if anyone var had this kind of problems with the s12?


My goal is to get around 300whp with this set up and use as much Nissan OEM parts as possible to make it a sleeper and road legal.

I was hopeing to get some good answers or input abot this set up and how you solve the timing gear issue.

Thanks

/Jesse Westerlund -Sweden

[s13eater]

what power rating is the turbo ? have you had any head work done ? have you uprated the cam ? what boost are you planning to use to get 300 rwhp ? i would also get rid of the afm and use a proper managment system. just i've been there years ago and got over 300bhp.

[Westerlund]

The gt2860 is rated at 340bhp on regular gas, so on E85 i dont se 300 at the wheels as an issue.

As mentioned abowe i will probably re-grind the cam, but no big head work, just clean it up a bit if porting is not nessecary?

When it comes to boost i will run what the turbo kan produce.

I was hopeing that a piggy back would be enough as this is my "budget build" i have a R33 4 door with a full drift set up, driftworks knuckles, dual rear calipers, adjustable rods etc and building a forged RB3026 for it at the moment with a Link g4 extreme engine management system and will be around 600whp so that car eats up most of the money.

So im trying to keep this on a smaller budget right now.
It's hard to find any good info about the 8 valve head, how much HP people have gotten out of them, where the stock cam says stop etc?

I also have a RB25 N/A with ITB's in progress that might end up in the s12 in the future.

I will start a project thread about it later but i have to re-write everything in english first.

[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.

[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