4agze + SC14 = Dissapointing power.

[Munki]

Hi all

I have recently rebuilt my 4agze with a sc14.It is in an ae86. It is running an adaptronic computer, a front mount with 2inch piping (over motor style) and a larger pulley (165mm i think). ABV is retained and modded. Exhaust is 2 inch.

On the dyno it made 115rwkw. The boost is 12.5psi (does drop off somewhat at high rpm)

The previous motor, same specs running 10psi on a SC12 on a sad bottom end made 110.5rwkw. Same dyno and tuner.

On the dyno we measured the exhaust backpressure and it was high (6lb from memory) so we disconnected the system from the cat back, it made 3kw more. Took the cat off and ran extractors back no change.

Took the air filter off and the power went backwards. I am stumped as to why there is so little power being made with the fresh engine and bigger blower.

Things that i have thought of.

-The piping from the sc outlet could be improved (quickly welded bend has lip on inside)
-The intercooler is too large?(unlikely) 300x600x70mm
-the throttle body is too small (std 50mm)
-the engine is still tight (done almost 1000km now)

I have seen a few similar setups get around the 130kw mark.

any ideas would be appreciated

cheers

Daniel.

[old_mr2]

Is the SC belt nice and tight? Does your intercooler have sufficient airflow?

[privatealpha]

Is the SC belt nice and tight? Does your intercooler have sufficient airflow?

Ive made 160kw at the wheels on the standard 4agze top mount, so any intercooler is probably better than that and will have enough flow.

[mullett]

seems very low. Is the motor assembled correctly? Mine GZE had one of the cams out by a tooth for a while, ran fine, but was very flat...Also if you've got aftermarket cams, get some cam gears. My GZE with 272 wades made about 100rwhp with an SC14 with stock cam gears, 180hp with adjustables adjusted...

-RM

[Munki]

cheers for the replies.

The supercharger belt seems nice and tight, but i can put some more tension on it. The cooler is a front mount behind the standard bumper, not ideal for airflow but not so bad.

Initially the cam timing was out a tooth and a piston stop check was done to identify true TDC and the cam timing adjusted to suit. It made 100rwkw at 4500 then fell over with the cam gears advanced one tooth. The cams are stock smallport with std gears. The motor seems fine and revs freely and is very smooth, but it feels no faster than the previous setup.

im really stumped.

[Munki]

could my sc14 be tired?

[andrew_mx83]

compression test?

[Duk]

-The piping from the sc outlet could be improved (quickly welded bend has lip on inside)
-The intercooler is too large?(unlikely) 300x600x70mm

You don't need an intercooler this big and it will be hurting your boost pressure.

-the throttle body is too small (std 50mm)

The standard 4AGZE TB is way to small! Think of it like this, would you use a 50mm TB on a 2.2-2.4 NA litre engine?
Look at NA cars that are making the kind of power you are hoping to make and use the same size TB.
I tested my standard pulley, standard SC AW11 and it would pull 4"Hg (Mercury) at 6500rpm trying to breath thru the standard TB. That's 2psi, or if you like, the SC was being filled with 12.7psi worth of atmospheric air pressure instead of the proper 14.7psi.
Vacuum at the inlet of a positive displacement pump cause cavitation. That why PD SC's use bypass valves for low throttle openings. Cavitation causes noise and heat (as well as wear) to be generated.

[Cuts]

still got the sc12? chuck that back on and do a run.

how much does the boost drop off at rpm?

dyno sheet?

you say the engine revs free? compression test?

i know you did runs without one but ide say ur zaust is a little small too.

[Adsport]

your pipework and throttle body is what is letting your setup down. you MUST run 2.5" the whole way to get the optimum out of an SC14. I have a bit of technical data and trial and error testing in my AW11 thread located below in my signature.

[mookschank]

your pipework and throttle body is what is letting your setup down. you MUST run 2.5" the whole way to get the optimum out of an SC14. I have a bit of technical data and trial and error testing in my AW11 thread located below in my signature.

Adsport, are you talking about 2.5" pipework prior to the S/C to airbox? or intercooler piping? or both?

[Duk]

Adsport, are you talking about 2.5" pipework prior to the S/C to airbox? or intercooler piping? or both?

Any pre TB pipe work should be as big as possible but without steps at changes of diameter.
I'd use a 60-65mm TB but you are limited by room for the actual TB to SC plumbing.
A 4AGE TB can be bored out to 60mm but the factory plumbing is limited to about 55mm. The difference in cross sectional area between the 60mm TB and 55mm plumbing is taken up by the TB shaft almost perfectly. I've not used this tho, as I didn't need to
There are still to many bends from the TB to SC .
I'm planning to use 2.25" SC to intercooler plumbing and then 2.5" intercooler to manifold plumbing, but that's my twincharger set up.

[Adsport]

Adsport, are you talking about 2.5" pipework prior to the S/C to airbox? or intercooler piping? or both?

on both sides buddy, i've done a few SC14 installs now and as much as people try to use small piping to stay to a budget they never get what they are after until all of the pipework from the throttle to the motor is at least 2.5". my setup was good for over 200hp at the wheels and i was using 2.5"

also +1 for Duk's comments.

[trdee]

Vacuum at the inlet of a positive displacement pump cause cavitation. That why PD SC's use bypass valves for low throttle openings. Cavitation causes noise and heat (as well as wear) to be generated.

can you link me to where you got this info from?

[Duk]

can you link me to where you got this info from?

Nope, I learned at trade school (Air compression and distribution), but it would be out there somewhere.

Munki should put a vacuum gauge between his/her TB and SC and see just how much restriction the poxy little TB really is.