What would you build?: High comp/low boost, Low comp/high boost

[page02wrx]

Hey fellas'

Probably closer to this or even next winter I'm thinking about picking up a CA18DET longblock from an importer... from there tearing it down for custom forged rebuild, and some head work....

But anyway, I'm debating on how to do the rebuild... I've already done the big turbo on a low compression engine (WRX 8:1)... so I'm not sure whether I want to keep this the same or not, but I want some opinions.

My two clashing ideas:

This is what I was set on doing so far8:1 compression, gt28 turbo, 450cc's, Tune for 17-19psi on pump.Advantages: More boost saferDisadvantages: No torque AT ALL

This is my other open option, I just don't know what turbo to use or anything like that10.5:1 compression, 450cc's, Tune around 7-9psi.Advantages: Low end torque and fast powerDisadvantages: Have to keep the boost low, and it is potentially harder to tune safely.

[Bwana]

A good standalone will be an absolute must if you want to run high compression. I'd suggest you chat with Ryan (float_6969) about it, he's running a high compression engine.

[page02wrx]

A good standalone will be an absolute must if you want to run high compression. I'd suggest you chat with Ryan (float_6969) about it, he's running a high compression engine.

Yeah high compression is a bit harder to tune, I think I'll be using megasquirt and a local shop hybrid dynamics to tune it.... if I go with the low compression build I can cross out the megasquirt and just have it ROM tuned

[boost_boy]

The CA is not that horrible when it comes to low end torque. Running with 8:1 compression will be just fine. Don't get into the worrying about the torque just yet. Build one first and then make a determination. The CA wasn't meant to be a torque monster below 3,000rpm, but with the right set-up, you still can kinda get the best of both worlds. The transition from 1000-3000rpm is barely noticed because of how fast it revs out. If you haven't done any upgrades, don't expect too much.

Dee

[r34 gtr]

i find that high boost, low compression is very fun with the little ca18. it is very, very different from the high boost/low comp ej205. the subaru is something like "whooooooaaaaah" where the ca18 is like "....hmm....whooooaaaaAAAAA jesus this is sketchy!!" my friend will attest, and he owns an 02 wrx.

[page02wrx]

Yeah I'm leaning more towards low compression and high boost also....

But for my goals then, would the stock CA18DET engine handle them? I'm only planning on 250whp.... but I've heard mixed reviews about the CA18DET engine.... I know it has a 8.5:1 compression, and thats about it. I'd just put a gt28r on it, 450cc's, pay hybrid $500 for a new ROM, and be done with it.

What do you guys think about the stock CA18DET? Also is any of it forged? Is the block open or closed deck(or semi-closed)? I know things like my Subaru has forged rods factory, but its open deck.

I would like to do cams though

[boost_boy]

I think Subaru is the most low-key Japanese car company, but their cars speak loud and stand out. I have a friend that had an 2005 Sti and that thing had gobs of torque down low. It wasn't a big revvin' car, but it had balls. I raced him with my turbocharged elantra and gave him hell. He tried to race our current sentra on the end, he lost badly. He raced my other friend's RSX and laid waste to it. I raced the same RSX with my elantra and smoked it. I raced the RSX with my current sentra, what waste of gas. But it was all in good fast because they wanted to see just how fast my sentra really was (They found out).

The reason I'm posting onthis thread is to help some of you understand what type of engine the CA18DET really. It likes to be revved and it does most of it's damage just past 5000rpm and weakens around 7000ish rpms (depending on mods). This video I'm about to link-up is an oldie, but it was done when tuning was new to me, the CA18DET was stock, I had a hybrid T25/T3 turbo, an open diff, my friend's 95 200sx tires, and SDS em-2 standalone pumping MSD 50 lb/hr injectors, and keeping in mind that I'm not the best drag racer around, either: http://videos.streetfire.net/s...6.htm

The WRX had a cat-back exhaust as far as I can see and the driver was a Jamaican guy that was very shocked when I not only beat him, but I told him it was a CA18DET. That was then and that car was a lot weaker than the car we have now. I have not done better than a 14.2@111mph and this was back in 2004 and haven't had the sentra back on the track since.

Dee

[page02wrx]

Thanks dee

If you have an AIM name or Email, I would appreciate it if you could Email it to me, that way I can ask you questions directly. I have a lot of them, the ca18 is a whole new animal compared to my ej207

[boost_boy]

You got mail!

Dee

[float_6969]

I think the appropriate question to ask is what kind of car do you want to build? For 250hp, you could really use stock internals with out the CA batting an eye. You could also bump the compression up to 9:1 and not have too much trouble tuning, although I don't think a ROM tune is going to cut it. I'm running 9.5:1 and on pump gas the tuning is VERY hard. The difference between a cool day and a hot day is enough for me to have to turn down the boost.

If you do plan on going with the high compression route, learn from me and plan on not only a standalone, but water injection as well. I know that I'm loosing power to retarded timing right now and I know I could fix it with reduced intake temps.

As for low compression, for 250hp, I wouldn't bother. The stock 8.5:1 compression is fine to 300hp pretty easily on pump gas.

[slidecrave]

figure this is pretty on topic to what hes asking so i'll ask it here..

for getting 300whp i've heard the internals should be fine and running the same setup he mentioned.. but im curious at this point would replacing the cams or alteast getting them reground lets say 270 8.8/9.0mm lift (since i see these are the ones for sale up top) what will be the big benefits in doing this, in responds to low end power and throttle response and where will it be possible to still get power out of the higher rpms band before power drops. Also around this power range i've heard that you could still run a rom tuned and be fine or would you recommend getting something more. Thanks

[Secret squirrel]

local shop hybrid dynamics to tune it.... i

you kno eric and the boys down at hybrid?

sorry to thread jack.

they sent me a nice photo the other day.



Id like to see how your tuning goes with them. i might venture down there to have them take a stab at mine.

SS

[johngriff]

So many things.

Where did these are the ONLY TWO CHOICES come from?

Why cant you run "high boost" with "high compression"

What even dictates "high boost" and you desired result.

Any halfway decent standalone will be able to manage "high boost/high compression".

ExTemp/FuelOctane/MaximumTq/Timing

You could pretty much tune anything to anything within these parameters.

I would size engine compression vs. Exhaust housing and wheel choice.

I also think that the "high compression must be low boost" myth is a myth born out of people bolting turbo's to n/a cars, WITHOUT ADJUSTING THE TIMING MAP.

Hybridynamics is a GOOD shop. I would consult them with your goals, and they will lead you to water.

[page02wrx]

So many things.

Where did these are the ONLY TWO CHOICES come from?

Why cant you run "high boost" with "high compression"

What even dictates "high boost" and you desired result.

Any halfway decent standalone will be able to manage "high boost/high compression".

ExTemp/FuelOctane/MaximumTq/Timing

You could pretty much tune anything to anything within these parameters.

I would size engine compression vs. Exhaust housing and wheel choice.

I also think that the "high compression must be low boost" myth is a myth born out of people bolting turbo's to n/a cars, WITHOUT ADJUSTING THE TIMING MAP.

Hybridynamics is a GOOD shop. I would consult them with your goals, and they will lead you to water.

Well you have to take your current static compression vs. your boost in bar to understand exactly how much effective compression you'll be running at full boost.

On a motor running 1bar of boost (14.7psi), at full boost you have now DOUBLED your static compression. So if I had two motors, one with 8:1, another with 11:1, 1bar of boost would mean 16:1 effective compression on my 8:1 motor, while 22:1 on my 11:1 motor. BIG difference there. Thats why there is no such thing as high comp/high boost in most cases on a stock motor.

[johngriff]

See you way jumped the gun by going all the way to 11:1.

Plus 22:1 is still manageable with good timing.

The best question is what output and spool time are you seeking?

[page02wrx]

See you way jumped the gun by going all the way to 11:1.

Plus 22:1 is still manageable with good timing.

The best question is what output and spool time are you seeking?

Well by high compression I meant more like 11:1... 9.5:1 isn't nearly at all worth it at least I dont think so.... if I had the choice between 9.5:1 or 8 I would do 8. 22:1 is still manageable yes but your timing would have to be severely retarded, to the point where you wouldn't be making the power you should... at least on a STOCK motor.... a built motor... which is what I would have, is a completely different animal when it comes to high compression.

And high boost to me is 20-22psi on pump... which is what I was running on my subaru..... not 1bar, 1bar was a mathmatical example....

I think I"m just goin to keep the stock motor... and possibly buy a gt28r, drop the 450cc's in, and pay hybrid for a tune.... I think that would be my best route to choose with my financial status..... As much as I would love a ca18 revving to 10-11k, 11.5:1 compression, 6psi and straight c16 gas..... The stock motor is more feasible for me at the moment.

Not to mention next summer I'll be buying an ls1 GTO I hope.

[r34 gtr]

so you are running the 207? thats quite a different motor from the crappy 205 we are beating the hell out of. the 205 gets the same amount of boost though, and it hasnt complained. the v7 longblock is quite the beast.

the high compression low boost thing i huess depends on how you take it. if by high boost you mean 30+psi then yes i can see why you would be wanting lower compression. anything below about 20 should be doable with a decent engine management setup. 10.5:1 and 20lbs would be fun as hell, but i would definitely run a water/meth injection setup. hell, i am considering it now! i mean, its an easy way to get some real reliable power from the engine.

[page02wrx]

so you are running the 207? thats quite a different motor from the crappy 205 we are beating the hell out of. the 205 gets the same amount of boost though, and it hasnt complained. the v7 longblock is quite the beast.

the high compression low boost thing i huess depends on how you take it. if by high boost you mean 30+psi then yes i can see why you would be wanting lower compression. anything below about 20 should be doable with a decent engine management setup. 10.5:1 and 20lbs would be fun as hell, but i would definitely run a water/meth injection setup. hell, i am considering it now! i mean, its an easy way to get some real reliable power from the engine.

Actually I was looking at buying a v7 longblock while typing that and hit the 7 instead of 5.... I'm still on the stock block lol, I'm still cast pistons and open deck sadly

I wish I had the jdm v7 though (((((((((((((((

Well stock setup I think will work just fine for me for a while.... till i decide to be like everyone else and do an sr20

[dash]

every impressive street ca18 I've seen ran low compression/hi boost.I consider a small displacement motor a 'standout' based on the torque it makes rather than peak hp... don't care for the 400hp/300tq.One of my favorites was bigtones old setup that engine dyno'd 496hp and a solid 474 ft-lbs tq, stock intake manifold too.

I've seen a couple 4ag and 2.6 starions run 25-28psi on "pump gas". I'd like to possess such tuning skills myself