Is it ported? Questionable driveability
 

Hello all 83 12a full exhaust and a 45 DCOE that was apparently street ported.

This is my 4th first gen but the first one I ever got to put some driveability miles on. I questioned if it was actually ported when I bought it and I'm unsure if there is a sure fire way to tell if it is with out breaking it down.

It idles kinda lumpy and best at around 1000 rpm. The driveability between 2000 and 3500 rpm is very jerky like it would be in any manual car in to low of an rpm. Anywhere above 3500 it screams and runs great. I'm interested if this is the nature of a street port or if I have some tuning to do.

Any help is appreciated

How familiar are you with DCOEs?

Stumbling between 2-3.5k could be an incorrect emulsion tube. Around there is when it transitions from the idle to main jets.

It may not be ported, it could just be the carb tune. I bet it has a wrap around intake as well? You may be able to take the header off and look at the exhaust port shape to get an idea if its ported.

Could also just be a vacuum leak or failing brake booster. Even a large street port should cruise fine at 2,500-3,000 RPM in traffic. Below 2,000 is another story. Maybe toss it on a dyno and see what kind of power it makes. If you manage to make over 110 to the wheels, it's been ported.

Wrap around intake indeed I'll take the Jets out and see what's in it at least see if it matches up with the "norm"

There is a mobile dyno at an upcoming show might be an easy test aswell

my peripheral port has near stock drive-ability, the carb tuning matters a LOT

Since the masses seem to point more to carb issues.

I played with mixture first I took a 1/2 turn out on the mixture screws and it got alot better.

So checked the Jets out my current setup is.


180 main
F11 e tube
175 corrector
65f9 idle
65 pump

This seems like a fat idle and a lean top end from what other setups I've seen posted

Thoughts?

it does seem like the idle is a little big, although it should run ok. 180 looks ok to me too. the 175 corrector looks really big, and i'm not a fan of the F11 Etube (Weber has a Etube to engine size chart, F11 is for a vw)

Strapped down to a dyno at a local track event today, car pulled 123.4hp. And 98tq

So with that said think it's just my bolt ons pulling that or a mild street port?

My stock ported 12A (OEM, never cracked the keg yet) with bolt ons does 134hp at the wheels. That said, its hard to say if its ported by a dyno number or not. Could be poorly tuned.

By ear and drive ability i would say the tune is pretty good now, timing is bang on no stumbles in the rev range, no excessive popping, plugs look good not burning not fouling, not stumbles anymore in peddle transitions. I really would like to get a wide band to really know.

I'm trying to get the base setup well and start planning by blow-thru turbo setup just want a good base to start with. i haven't decided to go with my Weber or a Nikki for the setup i'm leaning toward the Weber because i already have it.

dyno vid for fun

I think we can safely say it isn't an aggressive port job, but hard to tell from numbers off a random dyno with no baseline. I suppose if it is revving and continues to make power at higher RPMs you'll know if it's ported. The stock ports are going to flatline the power curve around 7000, a port job will keep pulling above that.

[QUOTE=chuyler1;12355016]I think we can safely say it isn't an aggressive port job, but hard to tell from numbers off a random dyno with no baseline. I suppose if it is revving and continues to make power at higher RPMs you'll know if it's ported. The stock ports are going to flatline the power curve around 7000, a port job will keep pulling above that.[/QUOTE

Very true. Mine produces no extra power above 7k.

I've attached the dyno sheet looks to level off at around 7k
https://cimg8.ibsrv.net/gimg/www.rx7...2e2a91227b.png

I think at this point, if you really need to know, pull the intake manifold off and shine a light down the ports. If they are polished nicely, someone has been in there.

However, if it has been ported, it's mild, or possibly something like the "74" ports that Jeff promotes which don't give you much more RPM but give you a nice bump over stock.

Thanks so much for all the help! I believe i have enough info to roll with for now and to start planning my blow-thru setup