13b engine
Can you hurt engine performance by porting engine?
Someone told me i would lose torque if i ported engine...
Its hard to think that porting could hurt engine horsepower...
But this is my first rotory engine...

 

Yes, you generally do lose some low-RPM torque from porting, but you gain high-RPM torque. This concept is somewhat universal -- it happens on piston engines, too.

-Max

 

always wondered the same thing, but never looked into it.

now i have another excuse for not porting my motor when people ask 'why didn't you have your motor ported?'.

chris

 

Not to steal your thread, but what about longevity? Do you shorten the engines life?

 

Mine engine is heavy ported and still with sequential twins. I didn't loose any low end, at least none that i can notice. But the high end is beautifull. It pulls so hard to the redline, it's great.

Amel

 

This is the kinda post that makes me glad I opted for the monster street port on my rebuild. Thanks for making my day!

 

Thats something i've always wondered but i would say yes since you getting more power with a ported motor.

 

am I the only one that thinks listening to a heavily ported motor idle on a daily or near daily basis would be annoying as ****?

 

Batmans motor is ported and has lasted awhile, mine is ported too and i didnt notice a drop in low end but noticed the gains on the high end , Its a good thing to get but wouldn't bother till you need a rebuild or have another reason to take the motor out. My motor is to new to say what the life expectancy turely is but i guess it would depend on what you have done and how hard you run your car. Ill ask batman his actual miles on his motor and report back

 

yes

 

The loss in low end isn't very noticeable for a street port. In fact, the car usually feels like it has more torque at low RPM than it did before because you have a fresh engine with good compression versus the tired, low compression engine that you probably just replaced. What is noticable is that the top end really comes alive. I was banging off the rev limiter a lot when I got my first street port because the car keeps pulling to redline, unlike the stock ports where the power starts dropping off earlier. It is definitely possible to gain "area under the curve" with a port job, and that is why people do it. But it only seems reasonable that there is some loss in power down low, even though it isn't very noticable with a street port. I don't accelerate hard at 1500RPM very often anyway.

Some reasons not to port:
- if you are saving money with a Mazda reman, it may not be worth the added expense to open it up for porting
- emissions are increased with porting, and while you can pass with a port job (I passed CA SMOG with a light street port), it does make it harder (I barely passed on my third attempt)
- you aren't interested in performance or never rev the car out anyway, so it isn't worth the expense or the chance of even losing a little low end power for a port job

But if you do like the rev the car out and want to make more power, a port job is definitely worth it. It feels great to make good power all the way to redline, and it will make your car faster. The loss in low end is hardly noticable (or even feels stronger, since the engine is fresh) from the driver's seat for a basic street port in most cases (as evidenced by the reports here), and the gains on the high end are very noticeable.

-Max

 

Street ports don't affect the reliability much, though anything that increases power will increase wear and decrease reliability to some degree. A street port doesn't have that much affect on reliability itself, though. You might be more reliable with a street port and 1 psi less boost than you would be with stock ports and 1 psi more boost making the same power, for instance.

The larger ports where there is a bridge or you cut into the water o-ring area can reduce longevity, but street ports don't have the same issues for the most part. Perhaps the only inherent reliability issue with a street port is that the exhaust port is bigger, which can stress the apex seal a bit more than a stock exhaust port (I can see some readers being alarmed by this, but read the next sentence before freaking out). But assuming the port is relatively mild, it probably isn't a huge difference.

-Max

 

I have ported some California cars with LARGE streetports on the stock twins with all the bolt-ons except we ran good cats. The cars were almost ZERO emission vehicles.

 

I have a street port and have seen no loss of low end torque

 

I find this hard to believe. Can you explain this?

 

It's not much different.

Now a bridge is a different story....

 

Doesn't the idle on a street ported motor bounce around a little bit. If that is so i get how it would be annoying.

 

My KDR streetport idle is perfectly smooth... it really depends on the size of the port, as to wether you get a lumpy/high idle.

Hard to say if I "lost" anything down low... but the reality is, most of what you do for power on these cars kills the low end to some degree... Because you're breathing it out, and relieving back pressure. remember how your car was smooth right through the transition... almost seamless... when it was stock? An then as soon as you slapped a cat back on it, there was a noticable"kick" after the transition?

 

Well, its fact. Mr RX-7 TT ported my motor 20k miles ago & it idles (spelling?) runs like a scalded dog. He's ported over a thousand motors during the past 23 yrs (he just did 2 more this past weekend...a 12A & a 13B I believe.....& he's never had a return ) I have a pretty aggressive port & I've had no issues (Smog or otherwise). Mr RX-7 TT was going to do Batman's, but I think the freight time was an issue or something. I'll email him & ask .

There is a myth about porting killing your emissions in Cali. Its not true. Just ensure you have a good Cat (stock or even a high flow), change your oil & plugs (if they are dirty) & take your car to Rick's Rotary. He'll check car to ensure its clean & coordinate the smog (even at a Test Only station). I had to change my O2 sensor & buy a new hi flow cat (my stocker was "toasted after so many years). My R1 passed as almost a zero emissions vehicle (had like "6" out of an allowable "85" reading for pollution - think it was Carbon off the top of my head?). In any case, your car should pass the sniffer with no problem if you do the above (clean oil, plugs, 02 sensor, & a good Cat).

See ya!
-Matt

 

If you can adjust fuel and lean the idle you shouldnt get the bump. A friend of mine with a monster street port runs a rich idle because when he punches it off the line he will get a bog for a sec if he doesnt run rich. Usually on a stock ecu you'll get that because the ECU thinks theres an airpump in there and more velocity vs more flow.

 

The big drawback to porting in my book is the extra noise - compare a street port on a stock exhaust vs stock port on a stock exhaust and the ported engine is significantly louder.

I found a noticeable difference at low rpm - 4th gear 20mph was fine on stock porting, but anything below 25 on the ported engine was to be avoided. It's not what you buy a performance car for, but for some people it could be a concern.

 

Sorry, I've got to call BS on this one.

 

Did you not read Yellow R1's personal acount that back up Mr Rx-7TT?

 

Yes, but you can't change what happens when you burn gasoline in an engine. I bet the results have more to do with this:

Everybody always knows where to take the car when you need it to pass and what to dump in the tank...

 

Since porting opens up the port size that would decrease port velocities and CFM's at low RPM's, thus hurting low end performance.

However, at high RPM's and during high boost in turbo'd cars the larger port size would gain in performance.

It's a catch 22.