12a CarTech drawthrough HELP!!
 

OK… So, I haven’t been able to find what I’m looking for by searching the forums. I’m just gonna ask everything at once.

I have an 85 RX with a 12a motor with remote (pre-79?) front mounted oil cooler and no beehive cooler. I was told the engine was street ported when I bought it. It currently has a Racing Beat intake/header and free-flowing exhaust with a Carter 500 cfm carb. The engine pulls very good… way better than my stocker before this one. I’m not sure on mileage on engine. It will hit 65 psi oil pressure by 2500 rpm (aftermarket gauge). I’m still using the stock fuel pump.

I will be installing a Cartech DRAWTHROUGH turbo setup… the model which does NOT retain the original intake manifold. The carb sits on a perch just above the turbo intake and flows out the turbo into a Cartech intake manifold. The turbo is a T25 and carb will be a 465 cfm Holley.

I had some questions and was hoping to get these answered. Thanks so much.

Is there a way to tell if a motor has been ported without completely disassembling the irons?

Distributor – Remove vacuum advance lines and retard total advance by 2 degrees?

Can I plumb the turbo’s oil drain line to the oil filler neck or does it have to flow DOWN to the oil pan or front cover?

What kind of max boost (psi) should I dare to play with? .. Resulting hp (I’m asking this because I read everything from 6-13psi on a stock 12a)

When should I be getting max boost (rpm)?

How hard to start are drawthrough setups?

When people say they are VERY hard to start in cold weather, what is considered COLD? (I live in Oregon and it was 28 degrees Fahrenheit this morning)

Should I try to monitor intake charge temp?

PLEASE… any help would be appreciated

Do you have the instructions for this kit? If not pm me and I will send them to you. I think most of your questions are answered there.

yeah.. I have the instructions.

https://www.rx7club.com/1st-generation-specific-1979-1985-18/cartech-bae-12a-drawthrough-turbo-install-instructions-780358/

These are "baseline" instructions. I was just curious if anyone out there has experimented with drawthrough boost in the way I listed.

The plumbing of the turbo oil line out im also interested in.

Is there a way to tell if a motor has been ported without completely disassembling the irons?
take off the intake manifold and look in the runner with a flashlight and stick your finger in it and feel around. lol

Distributor – Remove vacuum advance lines and retard total advance by 2 degrees?
remove advance and set timming to 10*btdc at full advance. lock the distributer as soon as possible.

Can I plumb the turbo’s oil drain line to the oil filler neck or does it have to flow DOWN to the oil pan or front cover?
oil drain has to flow down hill, no if and's or buts

What kind of max boost (psi) should I dare to play with? .. Resulting hp (I’m asking this because I read everything from 6-13psi on a stock 12a)
i wouldn't push it past 10 psi on pump gas without an intercooler. Yes you can use an intercooler, but you have to run richer to make up for the fuel puddleing in the intercooler, and it makes for some crappy throttle response.

When should I be getting max boost (rpm)?
t25 is tiny turbo max boost by say 3k rpm

How hard to start are drawthrough setups?
the hardest way to start a car, but if you get it tuned it should be okay

When people say they are VERY hard to start in cold weather, what is considered COLD? (I live in Oregon and it was 28 degrees Fahrenheit this morning)
it'll take at least three tries to get it started and you've got to warm it up for atleast 2 minutes before it'll be driveable.

Should I try to monitor intake charge temp?
sure why wouldn't you if you have the ability to.

If a were to go blowthrough.... Would i need a one-way valve for the brake booster vacuum line? Im assuming a brake booster cant take positive pressure.
With a blow through setup, how much psi would i dare??
Seems locking out distrituber and getting a boost referance FBR would work with blowthrough
Thoughts?

:stickpoke
Bump

Locking Distributer
 

I've been doing some searching on locking my distributer and found testomonials for welding weights or just removing springs.
If i remove springs and disconnected vacuum advance, would I just rev the engine and set total advance to 10 degrees advance?
Man... I really need to get a dial advance timing light.. ugh!!

Guys.. I really appreciate your input

if you lock no need to rev. Welding is a personal preference. If you don't and just remove springs, as soon as the car cranks the weights inside swing out due to centrifugal force. So when the car is running whatever you set it at is where it will be all the time. Lock that bitch and set the leading to 10 advance and the trailing to 0.

Keep your ten degree split. I know it sounds crazy and hard but it is not. I went threw all this last year on my turbo car.

If you went blow through you would need a check valve. Just ge3t a pcv valve for 8 bucks. Draw through is so out dated and in my "opinion" JUNK. Who the hell want's gas and air mixing inside a turbo right next to a 1800 degree hot side. Sounds like a bomb waiting to happen.

Locking Distributer at 10 degrees advance
 

So, on a 12a the leading timing mark is 0 degrees advance and the trailing timing mark is 20 degrees advance.

Would it be safe to assume setting timing at 10 degrees advance would be right between these marks? :wallbash:

Or, should I just buy a dial advance timing light, hook it on L1 plug wire, set it to 10 degrees advanced and turn distributer until pointing at 0 degree mark. :scratch:

Thanks guys

1st mark leading is at o 20 degrees behind that is trailing. Bump the dizzy clockwise till you get to 10 advanced. then do trailing 10 behind that. DOnt fuck with dial lights work for shit on a rotary. gonna have to remove the front pulley mark it 10mm from 0 for your leading mark.

which direction from the L1 0 degree mark am I measuring 10mm from? towards the trailing mark or away?

Is setting the 10 degree SPLIT necessary? Im sure I can find it through searching, but, do you do this adjustment via the vacuum pots?

It should not be hard to start if the carb is tuned properly and if you have a working choke. I have a draw-through supercharged setup and it starts right up and stays running easily in the mornings at similar temps to yours. However, once I start driving, my dumb electric choke sometimes kicks off too early and I have to keep it running with the gas pedal until it can idle on its own. Not a big deal, just a minor annoyance.

Read this and all your timing questions will be answered. http://www.yawpower.com/pultime.html Don't think about advance and retard as it just gets confusing... Just set timing at 10*before top dead center for leading and 20* before top dead center trailing.

Awesome!!
 

I remember reading that info a while back, but, couldnt find it again. THANKS

This will make setting my LEADING timing very easy.

But, for the TRAILING 10* split, do I use the same marks or mark my pulley to the LEFT of the 20* trailing mark?

Give me a V8 and I'm fine.. substitute 2 rotors and two spark plugs per rotor.. and it takes me a bit to grasp the concept.

This is a very simple concept. The trailing and leading are two completely seperate working ignition systems. The leading are the most important and the trailing fires after the leading just to clean things up... So when you are setting the trailing you're setting when it fires after the leading, so if you set the leading to fire at 10*btdc and you want 10* of split then you set the trailing to fire at 20*btdc... All split the split is measuring is the degrees that the trailing is firing after the leading.

I KNOW im prob over thinking this.
Im looking to do the weight spring removel dizzy lock, so, even at idle it will be full advanced.

Looks like I will be marking the pully to the right of the TDC mark (seen from front of car), making marks every 0.196" = 5* for the leading. Set LEADING timing to 10* than lock the dizzy adjusting nut. Than adjust the TRAILING advance pot until timing mark back on 20* TRAILING OEM mark???

Yes even at idle it will be at full advance. And yes. And no. Put the trailing so it lines up 10* behind your leading, so if you set leading at 10* BTDC you set trailing at TDC.
https://www.rx7club.com/attachment.p...1&d=1232746446

Hyper4mance2k... your awesome. Thats all I wanted, an easy way to visualize the timing.
I wonder why Mazda decided on a 20* split stock?
Seems most of the dyno numbers show 8-12* split is best for performance.

As an odd twist of fate, the circumference of the timing pulley is 360 mm, ergo, 1 mm=1* of timing. Skip trying to use an inch/foot tape measure and find metric tape that you can wrap around the pulley. Makes life soooo much simpler. Iirc, Yaw recommends a 24/16* advance at 3-4k rpm, which equates to an 8* split, not 10*, which is what most all rotarys have stock.

If you want accuracy, RB sells a replacement timing pulley that has much better marking.

Ok, my target boost will be 7 psi running 10* advance LEADING and TDC TRAILING (locked dizzy). I will be running a 72gph 6psi fuel pump through a summit canister filter to a 465cfm holley carb. exhaust will be 2.5" through inline and tailpipe magnaflow mufflers.

Any recommendations on fuel grade? 87, 89, 92?

I know this is not a rotor motor bt it is a draw through setup. I can say from experince that the intake charge is ICE COLD on a cold start up. I am in Midland GA about miffle of the state and you could not touch the intake between the carb and Turbo and this is even after drivinig it for a while... Here is a pic of my turbo beetle.. Made 471 rwhp when it broke the right rear axle in a 3rd gear dyno pull at 5500 rpms.. Could have made 500.. And as far as putting an Intercooler on a draw through... No way in hell I would do that.. It is a bomb waiting to explode with fuel sitting there.

http://i17.photobucket.com/albums/b9...06004Large.jpg

dont listen to Scott about timing he has no clue on a turbo motor. Although he will say he does just listen to turbo people.

No shit 24* btdc = blown up car if you're turbo

lock it at 10 degrees total advance and your all good
p.s. that bug is sick!!!

More pics of the bug twisted one!