Grizzly

I know there is lots of Threads about this but what i want to know is i have a very large ported engine (inlet) and i used a template to shape the Exhaust ports, i have heard i should'nt open the runners out to much as it slows the gasses down and there fore slows the spool up.

What should i do? just smooth out the port and give it a light flow job or open it up?

Thanks.

Judge Ito

Remember the concept for porting." to open earlier and close later"...... What year engine u have?

Grizzly

I have a Series 5 T2, I have done the Porting useing a tempate what i need to know is how much i need to open the runners ?

Thanks.

Rotortuner

Make sure you only go down on it. Thats what they say. I have never ported a turbo motor but i have donw a couple of NA's. Any ways i would take it down just enough to round it out, say maybe about a 1/4 inch or mabe not even that much and then clean it up. You might also want to widen the existed portion a little too.

CJG

Grizzly

Sorry you dont get where i'm coming from. I have a Race Beat Template for the Port its self which is now cut i want to know if the Runner between the port and the manifold should be made alot bigger or will this mess up my Spool up? I have heard that the bigger they go the slower the gas flow is and there for there is a knock on effect with the Turbos spool up.

I have a very large ported engine and i want to know if my theory is correct (basicly i want to get the best power delivery i can)

Dragon

you cant really port much out of the sleve because it's pretty thin. when you look in from the exaust flange side of the port, try to keep the port itself about 1mm above the the sleeve so the gasses don't try to go around it..

RETed

Port the exhaust as big as you want...
The key is to gently form it to the shape of the stock sleeves.

Someone in here has stupid-crazy BIG exhaust ports (removed stock SS sleeves)...either RICE RACING or crispeed!&nbsp They don't complain about slow exhaust gases.

I'm going to recommend not to port "up" on the exhaust due to increased overlap.&nbsp I don't want to turn this into another BP or not to BP thread, but for a street motor, don't increase overlap...



-Ted

RICE RACING

Here are mine.

ONLY do this if you are going to run a 1.15 a/r (t04 family) or larger, I run a 1.32 with 3" exhaust and race tunned length manifold and it works "realy" well.

RICE RACING

My engine pulls higher average boost with the larger exhaust ports, while also delivering maximum boost at a higher rpm point, extending the "usefull"rpm range of the engine.

Peak boost before the Radical port occured about 6700rpm, After the port job peak happens at 7400 to 7600rpm, Average boost from 5500 to 8500 is higher with the big exhaust port. I.E. Larger power band.

RICE RACING

My port is up as high as you can go in the rotor housing, and as down as far as you can go. This increase gives you the overlap that you need to increase the rev range of the engine and hence make more power with less boost, not only does it lift the peak power point but it does make the engine have more of a "range" that will suit the factory gear box ratio's much better.

This port works fine with a road exhaust, almost legal But I do believe it would suffer with the small a/r ratios that seem so popular in the US, I would use a 1.15 minimum on this type of engine, to get the gains in VE that this exhaust port will allow.

Grizzly

Rice if you dont mind me asking what intake ports do you run with that sized Exhaust?

I'm running PB but i am abit paronoid that i made the Exhaust ports to small. At the time i did'nt know to much about the hole porting game and just got a Race beat Template and opened them to that size blended it in and that was basicly it.

So running a 1.15 devided T04s RB Turbo with a PB would be ok with larger Exhaust ports? at the moment mine look tame (slightly bigger than an Extended port set up) but with large Extended port Primarys and Bridge Secondrys. Having said allthat my low end power is good if i opened the Exhaust up would that raise the low end usable power?

Thanks for the replys.

RICE RACING

I run "large" street port Intake for primary and secondary, both have same opening and closing times.

You do loose low end power and responce below 4500rpm when you use the largest Intake port possible and largest Exhaust possible, but you gain in the important ranges from 5500 to 8500 you will not make better power, These same rules apply to PB FB and PP and FPP turbo engines....There is alot of "usable" power to be had in the exhaust porting, but it realy needs a first class exhaust header to work and not be choked by the turbo/wastegate.

Basicaly with turbo rotaries in my experience (my only experience is with rotaries !) I have found that if you let the engine breath i.e give it overlap and let the exhaust work then you will have a broader power band, you in EVERY case end up flattening the torque curve of the engine which results in much more linear power delivery and the bonus is that you will make it higher up in the rev range so you will not need as much boost (less stress on turbo) while still staying with in the mechanical (engine speed) limits of the engine. It is harder and there is more work to do in blueprinting the engine but NO special parts are required for the block just some detail clearancing and thats it.

I have had alot of different engine configurations and would never run an engine (If I had the choice) with std or near std mazda spec for the opening and closing of the exhaust or intake ports, they are just too mild and are designed to give good low speed economy and work with restrictive factory turbos.

For a side port (single turbo race/street car with full mods) get as much overlap as you can, i.e. raise the exhaust port.....you will not regret it, or rather you will regret not doing it

Grizzly

Ok when i did the Intake porting i went out of my way not to move the Overlap as i belived this would make the car undrivable (power band very small) as for the exhaust as i say its a Racing beat Template job as i thought they had more experiance in this sort of thing, since then i have read up alot about the Templates and found they are very mild and the Exhaust one i used is basicly is to complement an Extended port.

How can i tell how far i can take the Exhaust port?

I have not had a problem with low power as i have a Roller Bearing Garret Turbo and it spools up very quick so i have good responce etc.

Thanks for you Time its nice to talk to a realy Experianced Rotary Tuner.

peejay

Oh no, increasing the overlap will do wonders for the torque of the engine even at low RPM. (In my experience) Next time I'm taking it ALL the way up, not just high enough to go flush with the sleeve

I do have a question on those HUGE exhaust ports though... wouldn't the nearly flat closing edge of the exhaust port be detrimental to apex seal life? If I'm way off base let me know...

RICE RACING

It looks flat, but there is a small curve in the top so the apex seal does not shut on a flat edge....If you look at the centre of the port the top edge is angled down about 3 to 5 deg to the outer edges.

It does not need to be a curve like you see some engine builders use, having a flatter top increases the energy of the pulse generated by the port closing which improves the VE as well.

Grizzly

Do you know of anywhere i can read up on Marking ports out or is it an experiance thing (do it a little at a time)

Thanks

moespeed

RICE, you got the biggest exhaust ports I've seen on the net.
What kind of HP are you getting with the above setup and with how much boost?
Is the 3' exhaust good enough or is there a difference running a bigger exhaust?

RICE RACING

I have posted my BHP figures before, but here are the current figures (SAE corrected) and in road tune with 3" exhaust and single "legal" muffler NOTE these are engine power, not rwhp !

495 to 500BHP @ 8200rpm @ 1bar (14.5psi) gauge pressure.

560 to 570BHP @ 8200rpm @ 1.3bar (18.85psi) gauge pressure.

My peak boost happens @ 7600rpm and I have 95% of my maximum boost from 5500rpm to over 8500rpm.

At 4000rpm Engine makes roughly 10psi or 0.7bar boost, It is designed to be used with a GEAR BOX ! ...My spread of power is perfectly suited to the std T2 ratio's.

In a 1170 kg car when set a 1bar boost in does the following accel times (200mph final drive)

moespeed

F40 killer with stock drive train.
Looks like this setup for the street is dialed in pretty well. Besides being louder and ilegal, wondered if a larger exhaust would have given better numbers. Have you ever tried larger and with what results?

RICE RACING

I used to quote my figures based on no rear muffler, just straight 3" pipe ! It gives about 15 to 20bhp increase at 1bar and around 20 to 30bhp at 1.3bar.

Highest power I have recorded on my car with 9.0:1 compression street port is 590BHP (I have gotten higher with more compression and combination port due to better BSFC), this is the limit of the turbo on this car as the air flow at the inlet is around over 750KPH ! and the inlet air becomes quite hot and the turbine is almost over speeding.

The general figure over ther for dynojets is 15 drive/tire etc loss so 500rwhp is the maximum I have got from this combination.

Turbo is the following spec RICE TO4
compressor R11 inducer 2.311" Exducer 3.0" tip width 0.288" Housing 0.7a/r (larger of Garrett with cast steel backing plate), water cooled center bearing housing.
Turbine P trim "back sweep blade" config. Housing 1.32a/r divided.

moespeed

I would like to know other than some (4.7???) rear end gears what turbo you would run on this setup if you had to run against those 9 second street Rx7s in the 1/4 mile?
Some of them are running big boost and NOS.
Would you run the same turbo or would you run something that flows better at higher boost?

RICE RACING

Me personally, and this is my "personal" opinion.

For drags I would run NOS, I have used Larger Turbos (and I mean LARGE 100mm compressor inducer!) on different engines and they ALL lag pretty much to the point that you need a little NOS if you were going to get the maximum LAUNCH speed from your car, once you are going (road racing) this is not an issue as there is lots of gas flow speed generated by the load on the motor.

Here is a quote I have used a few times to other people who ask me similar questions about this ALL the time

“ Clearly, the speed of the turbine is the speed of the compressor. Centrifugal forces increase as the square of rotational speed but air is light stuff and in practice the compressor has to run at high speed before anything much happens in the way of significant boost. At low to medium engine speed boost will be modest, particularly as the inlet pressure build up has to be insufficient to cause surge. However as revs rise pressure will start to rise disproportionately and power will climb quickly and steeply. In the worst case there will be a sudden inrush of power that the driver will find very hard to cope with. Hence the importance of a waste gate (to run lower boost!) if a more civilized engine is desired “

Now with NOS you can feed in lower amounts like 50bhp or 75bhp from low revs to help the turbo “come on” but you can also add another 50 to 100 in the top end 5500rpm, this would give you the best of both worlds, You eliminate the problems associated with running a LARGER turbo I.E. Narrow range when run with street port, Is better with PP !

So with my combination in theory you would have a 590BHP engine in just turbo form with a 3000rpm power band (5500rpm to 8500rpm) then you can add 50bhp NOS at low revs and another 50bhp at revs above 5000rpm to give you a total of over 700bhp or around 600rwhp ! (it would be higher than 700bhp cause of the major charge temp drop with NOS). This is more than enough to run a low 9sec pass in a RX7, assuming traction !

If I got into drag racing this would be the specification I would run on the engine, It is cheap and all of the hardware is there bare the NOS setup.

There are MANY ways to skin a cat though, and this is only one solution to your drag racing question !

moespeed

Thanks for the info.
If you think of other ways to skin a cat I would love to hear them.

Rotortuner

Hey rice,

Ya i get what your talking about when you replyed to my post. And yes i aggree that overlap in not a bad thing. I just made a set of p port housings and of course with those we have big time overlap. I will try and eventualy post some pics, but i am going to assemble the engine this thurs, and i dont have a digital camera so i cant get any this time. My ports i did not go down at all cus my theory one the NA stuff is that going down on them you lose more motor that way, so i went out and up a bunch almost as much as those that you posted. In fact they are probably the same but yours are a little bigger because you went down on yours also. Oh by the way mine is a 12a not a 13b. I dont use any templates when i do my stuff, but mine are rounded on top not nearly as tight radioused as yours, but definitaly interesting to see other theorys and techniques. And if you did not catch it i sleeved these housings myself, not factory housings.
CJG