Polishing Rotors - Pros and Cons - Page 2

vex · 03-16-2009, 09:32 AM

I recently cleaned my rotors by hand and noticed they had a yellow coating on them. To top it off one rotor seemed to have a textured face while the other did not. Not sure if that plays a role or anything, but i thought it interesting.

To_Slow · 03-16-2009, 09:35 AM

Bling Bling... looking good

Quote:

Originally Posted by NoDOHC

A few questions:

What would you call this? (Street port? Stock port?)
Attachment 4716
Attachment 4717

The intention was to avoid changing port timing while providing a nearly consistent cross-sectional area for the primary and secondary runners and ports. I am not sure if this is still a stock port due to stock port timing or if it is considered a street port.

Here is a picture of the finished rotors (I would post more, but it is too much work resizing them).
Attachment 4718

JunpoweR · 03-16-2009, 03:04 PM

Some rotors have grooves and some don't
when removing material from the rotor to polish, I believe a balancing is in order before putting them into an engine.

RX72NR · 03-17-2009, 05:01 AM

For ceramic coating of rotors, housings, or irons check out JHB Performance in Canada. Here's my rotors that are going into my next setup. These have the cermet A applied to them.

NoDOHC · 03-17-2009, 10:03 PM

Thanks Atkins Dan, I wasn't sure of the exact definition of each.

I intend to balance the engine JunpoweR, don't worry about that.

RX72NR: Why do you have that portion on the rotor machined off? Is this intended to dramatically lower compression? I don't think that you will get much combustion out at the edge of the rotor like that, too much quench area. Did you do that only to the one side of each face? What kind of power are you looking for?

I am only looking for 300 at the wheels. (Should be attainable with standalone ECU 550/720 injectors and a good FMIC). I think I will use the stock turbo for now.

Atkins Dan · 03-17-2009, 11:11 PM

NoDOHC

Your welcome and hope the info helped..

Dan

RX72NR · 03-18-2009, 05:12 AM

My goal is around 500 h.p. on pump gas. The rotors are beveled/ flame relieved. I'm not a guru, maybe someone can chime in and explain the theory and benefits. I've got some NRS 3mm grey ceramic seals and springs going into the build. I'm thinking of having the housings and irons cermet A coated as well. Here's a pic of my twins...

neit_jnf · 03-18-2009, 10:24 AM

The rotor bevels change the intake port timing, I believe earlier opening actually helping the engine breathe like a bridgeported one but without the drawbacks.

RX-8 rotors have that from the factory but smaller.

NoDOHC · 03-19-2009, 10:44 PM

Ahh, I see now. That is a really cool Idea (I even complained about the distance between the side seal and face of the rotor while analyzing my port timing).

How do you balance the engine like that? I can see that only half of each rotor face was removed, but still the counterweights will have to get a lot lighter. I guess you can drill them a lot.

Thanks for the info (maybe I can do that next time).

500 Hp, wow!

BSC Motorsports · 03-20-2009, 08:02 AM

I wonder if polishing the rotors has much effect on atomization? Alot of piston guys will sand blast their piston tops for atomization. Due to the path air and fuel take going into a rotary I doubt the effect would be the same, but I'm curious.

Brent

NoDOHC · 07-10-2009, 11:16 PM

Update:

Sorry to resurrect this thread, but I have 4400 miles of driving to discuss.

Short story, Brent is 100% correct. The engine does not like high vacuums at lean mixtures at all. I have to run about 12:1 at idle to make it run. My fuel economy is down too (38 mpg instantaneous at 70 to 34 mpg instantaneous at 70, about 29 mpg on a tank). Most of the loss of economy is the fact that at cruising vacuums (~50kPA) I can't go lean of stoic (I was running 16:1 AFR before).

Long story: Too many other factors involved to discuss power (4-port vs. 6-port, bored-out intake runners, heavily modded UIM, etc.) but the detonation resistance is insane.
The engine will not pre-ignite at all. I have never heard it knock (I am still running NA). I advanced my timing until flooring the gas made the engine deccelerate the car and I still heard no knocking noise (70 degrees BTDC).

After those miles (very few actually, in the grand scheme of things) it pulls 70 kPA of Vacuum at idle, makes 100+ psi on all faces and otherwise appears to be in good condition.

Interrestingly enough, the engine makes more torque at 2,000 rpm than the 6-port before it. (It makes a whole lot more torque at 7500.) All in all, I am very pleased with the 4-port NA (my first). Unfortunately, Idle torque is not very good at all, the torque curve doesn't even start until 1500 rpm.

The car is very hard to drive with a stage 2 clutch, 8lb flywheel and no low end torque.

classicauto · 07-28-2009, 02:14 PM

Quote:

Originally Posted by NoDOHC

Update:

Sorry to resurrect this thread, but I have 4400 miles of driving to discuss.

Short story, Brent is 100% correct. The engine does not like high vacuums at lean mixtures at all. I have to run about 12:1 at idle to make it run. My fuel economy is down too (38 mpg instantaneous at 70 to 34 mpg instantaneous at 70, about 29 mpg on a tank). Most of the loss of economy is the fact that at cruising vacuums (~50kPA) I can't go lean of stoic (I was running 16:1 AFR before).

Long story: Too many other factors involved to discuss power (4-port vs. 6-port, bored-out intake runners, heavily modded UIM, etc.) but the detonation resistance is insane.
The engine will not pre-ignite at all. I have never heard it knock (I am still running NA). I advanced my timing until flooring the gas made the engine deccelerate the car and I still heard no knocking noise (70 degrees BTDC).

After those miles (very few actually, in the grand scheme of things) it pulls 70 kPA of Vacuum at idle, makes 100+ psi on all faces and otherwise appears to be in good condition.

Interrestingly enough, the engine makes more torque at 2,000 rpm than the 6-port before it. (It makes a whole lot more torque at 7500.) All in all, I am very pleased with the 4-port NA (my first). Unfortunately, Idle torque is not very good at all, the torque curve doesn't even start until 1500 rpm.

The car is very hard to drive with a stage 2 clutch, 8lb flywheel and no low end torque.

Are you saying the polished rotor faces are helping reduce detonation? And that they are causing you to need to run richer in vaccum?

NoDOHC · 07-28-2009, 06:25 PM

I don't know for sure (too many factors). I did polish all the dry areas on the intake manifold to 400 grit and polished the wet (after injectors) surfaces to 150 grit. I also am running lower compression (I think 8.2:1 if I measured the water right). However at 40 degrees BTDC my 9.4:1 6-port sounded like a gnome was beating on my hood at 1000 rpm and this one will advance considerably past that (until the engine generates negative torque). I don't know if it is only due to the polished rotors, but that is what I am blaming it on.

Most detonation is actually the collision of two flame fronts. One is caused by the spark plug, the other is caused by a localized hot spot. By polishing the rotor I not only increased the heat rejection (think shiny handles vs. black handles in the sunlight) but I also minimized the possibility of localized hotspots (due to uniform surface finish, no protruding surfaces to absorb heat).

Actually I am very happy with the results on this engine, I recently discovered that the Borch handbook's advice to advance the timing until it detonates and then back it off 5 degrees is not very good advice on a rotary. I retarded my timing 30 degrees to 8 degrees BTDC at 1000 rpm and the car has surprisingly good low end torque (lugs to 300 rpm, no problem and will actually accelerate from there).

I will be interesting to see this engine with a turbo...

classicauto · 07-31-2009, 11:37 AM

Reason I asked is typically, knock in a rotary isn't heard for long. USUSALLY its not even audible before its blown. I've only ever once heard the death rattle for about 0.5 seconds in all the engines I've blown.

My other point was the need for richer mixtures in vaccum would indicate you've disturbed the efficiency of the combustion chamber. If you're having to run closer to stoich, or under it, to achieve proper power/good running then it means the combustion chamber isn't "mixing" the air and fuel as effciently as it was which would cause the need for more fuel to be present for an even burn (good running) when the spark lights off.

Whether it is the polishing, runner smoothing or otherwise I couldn't say for sure.

RETed · 07-31-2009, 12:16 PM

Quote:

Originally Posted by NoDOHC

By polishing the rotor I not only increased the heat rejection (think shiny handles vs. black handles in the sunlight) but I also minimized the possibility of localized hotspots (due to uniform surface finish, no protruding surfaces to absorb heat).
(lugs to 300 rpm, no problem and will actually accelerate from there).

I doubt this is the case...
I bet the rotor faces are already black with soot and carbon deposits.
You'd be surprised how well deposits after combustion will stick to surfaces.
Since this is a rebuild, the engine would've been burning inefficiently due to inferior compression from the seals settling in.
This is more than enough time to leave a fine layer of soot on the rotor faces.
Too bad we can't tear the motor down just to confirm this...

-Ted

03-16-2009, 09:32 AM	#16
vex RCC Loves Me Not You Join Date: Jul 2008 Location: Influx. Posts: 2,113 Rep Power: 19	I recently cleaned my rotors by hand and noticed they had a yellow coating on them. To top it off one rotor seemed to have a textured face while the other did not. Not sure if that plays a role or anything, but i thought it interesting. __________________ The Official FC Radiator Thread My Project Thread: Cerberus CCVT Virginia Rotary Group

03-16-2009, 03:04 PM	#18
JunpoweR Rotary Fan in Training Join Date: May 2008 Posts: 66 Rep Power: 0	Some rotors have grooves and some don't when removing material from the rotor to polish, I believe a balancing is in order before putting them into an engine. __________________ --^v--JunpoweR--^v-- "90 GTUs Crystal White GT35 WB TA Project "90 GTUs Brilliant Black Restoration 1984 GSL-SE Daily

03-17-2009, 10:03 PM	#20
NoDOHC The quest for more torque Join Date: Sep 2008 Location: Sheboygan, Wisconsin Posts: 855 Rep Power: 17	Thanks Atkins Dan, I wasn't sure of the exact definition of each. I intend to balance the engine JunpoweR, don't worry about that. RX72NR: Why do you have that portion on the rotor machined off? Is this intended to dramatically lower compression? I don't think that you will get much combustion out at the edge of the rotor like that, too much quench area. Did you do that only to the one side of each face? What kind of power are you looking for? I am only looking for 300 at the wheels. (Should be attainable with standalone ECU 550/720 injectors and a good FMIC). I think I will use the stock turbo for now. __________________ 1986 GXL ('87 4-port NA - Haltech E8, LS2 Coils. Defined Autoworks Headers, Dual 2.5" Exhaust (Dual Superflow, dBX mufflers) 1991 Coupe (KYB AGX Shocks, Eibach lowering springs, RB exhaust, Stock and Automatic)

03-17-2009, 11:11 PM	#21
Atkins Dan Premium Vendor Join Date: Feb 2008 Posts: 265 Rep Power: 18	NoDOHC Your welcome and hope the info helped.. Dan __________________ 82 SuperCharged rx-7 {my toy not the daily driver anymore now under restoration} 88 B2200 rotary powered with a 7inch Camden SuperCharger !RIP! Jan/4/2007 2001 626 5-speed 80k on the clock all stock {Truck replacement} 2005 MAZDA6 V6 WAGON now that is a pimping ride all stock for the moment.. Paid off WWW.AtkinsRotary.com

03-19-2009, 10:44 PM	#24
NoDOHC The quest for more torque Join Date: Sep 2008 Location: Sheboygan, Wisconsin Posts: 855 Rep Power: 17	Ahh, I see now. That is a really cool Idea (I even complained about the distance between the side seal and face of the rotor while analyzing my port timing). How do you balance the engine like that? I can see that only half of each rotor face was removed, but still the counterweights will have to get a lot lighter. I guess you can drill them a lot. Thanks for the info (maybe I can do that next time). 500 Hp, wow! __________________ 1986 GXL ('87 4-port NA - Haltech E8, LS2 Coils. Defined Autoworks Headers, Dual 2.5" Exhaust (Dual Superflow, dBX mufflers) 1991 Coupe (KYB AGX Shocks, Eibach lowering springs, RB exhaust, Stock and Automatic)

03-18-2009, 10:24 AM	#23
neit_jnf Boricua! Join Date: Jul 2008 Location: Puerto Rico Posts: 99 Rep Power: 17	The rotor bevels change the intake port timing, I believe earlier opening actually helping the engine breathe like a bridgeported one but without the drawbacks. RX-8 rotors have that from the factory but smaller.

03-20-2009, 08:02 AM	#25
BSC Motorsports The Newbie Join Date: Feb 2009 Location: Innisfil Posts: 17 Rep Power: 0	I wonder if polishing the rotors has much effect on atomization? Alot of piston guys will sand blast their piston tops for atomization. Due to the path air and fuel take going into a rotary I doubt the effect would be the same, but I'm curious. Brent __________________ www.bscmotorsports.ca

07-10-2009, 11:16 PM	#26
NoDOHC The quest for more torque Join Date: Sep 2008 Location: Sheboygan, Wisconsin Posts: 855 Rep Power: 17	Update: Sorry to resurrect this thread, but I have 4400 miles of driving to discuss. Short story, Brent is 100% correct. The engine does not like high vacuums at lean mixtures at all. I have to run about 12:1 at idle to make it run. My fuel economy is down too (38 mpg instantaneous at 70 to 34 mpg instantaneous at 70, about 29 mpg on a tank). Most of the loss of economy is the fact that at cruising vacuums (~50kPA) I can't go lean of stoic (I was running 16:1 AFR before). Long story: Too many other factors involved to discuss power (4-port vs. 6-port, bored-out intake runners, heavily modded UIM, etc.) but the detonation resistance is insane. The engine will not pre-ignite at all. I have never heard it knock (I am still running NA). I advanced my timing until flooring the gas made the engine deccelerate the car and I still heard no knocking noise (70 degrees BTDC). After those miles (very few actually, in the grand scheme of things) it pulls 70 kPA of Vacuum at idle, makes 100+ psi on all faces and otherwise appears to be in good condition. Interrestingly enough, the engine makes more torque at 2,000 rpm than the 6-port before it. (It makes a whole lot more torque at 7500.) All in all, I am very pleased with the 4-port NA (my first). Unfortunately, Idle torque is not very good at all, the torque curve doesn't even start until 1500 rpm. The car is very hard to drive with a stage 2 clutch, 8lb flywheel and no low end torque. __________________ 1986 GXL ('87 4-port NA - Haltech E8, LS2 Coils. Defined Autoworks Headers, Dual 2.5" Exhaust (Dual Superflow, dBX mufflers) 1991 Coupe (KYB AGX Shocks, Eibach lowering springs, RB exhaust, Stock and Automatic)

07-28-2009, 06:25 PM	#28
NoDOHC The quest for more torque Join Date: Sep 2008 Location: Sheboygan, Wisconsin Posts: 855 Rep Power: 17	I don't know for sure (too many factors). I did polish all the dry areas on the intake manifold to 400 grit and polished the wet (after injectors) surfaces to 150 grit. I also am running lower compression (I think 8.2:1 if I measured the water right). However at 40 degrees BTDC my 9.4:1 6-port sounded like a gnome was beating on my hood at 1000 rpm and this one will advance considerably past that (until the engine generates negative torque). I don't know if it is only due to the polished rotors, but that is what I am blaming it on. Most detonation is actually the collision of two flame fronts. One is caused by the spark plug, the other is caused by a localized hot spot. By polishing the rotor I not only increased the heat rejection (think shiny handles vs. black handles in the sunlight) but I also minimized the possibility of localized hotspots (due to uniform surface finish, no protruding surfaces to absorb heat). Actually I am very happy with the results on this engine, I recently discovered that the Borch handbook's advice to advance the timing until it detonates and then back it off 5 degrees is not very good advice on a rotary. I retarded my timing 30 degrees to 8 degrees BTDC at 1000 rpm and the car has surprisingly good low end torque (lugs to 300 rpm, no problem and will actually accelerate from there). I will be interesting to see this engine with a turbo... __________________ 1986 GXL ('87 4-port NA - Haltech E8, LS2 Coils. Defined Autoworks Headers, Dual 2.5" Exhaust (Dual Superflow, dBX mufflers) 1991 Coupe (KYB AGX Shocks, Eibach lowering springs, RB exhaust, Stock and Automatic)