Looking for some advice. I have never had this car to the track or have launched hard on the drag radials. Unless something comes up or it rains on Thursday, I will be heading down to Bradenton 1/4 mile to get some shakedown passes done in the 8. Obviously with street tires and lack of traction, I have never really feared any drive-train problems. Launching at a prepped track on MT drag radials is a whole other animal.

My plan is to have the 2-step up at 5500-6000, and will try and let the clutch out in a controlled manner until the car is moving and planted. Obviously my 60 foot will suffer, but I also don't want to blow my car up on the first launch. I assuming that any type of clutch drop will be instant kill to the axles or rear end.

Has anyone launched a rx8 on some sticky tires with any type of power? Can anyone attest to the strength of the rear axles or rear end? Appreciate any thoughts...

 

Axles seem to be the next weakest link after the stock 6 speed. The rear ends are quite hard to break.



I would think that you need to be careful dropping the clutch while really hooked up.....



I guess the good thing is that taking out an axle really doesn't do too much other damage The fun part is driving home.......

 

After paying $175 to have my car towed home one time from the track, I now have AAA gold and get 4 tows of 100 miles per year.

The clutch has about a 1/2-inch of engagement and grabs hard. If I leave on low RPMs, it will be a guaranteed bog and the run will have a dismal ET. If I leave on high RPMs, and get too aggressive with clutch, I surely will snap an axle because these tires hook. The only way I see that I can get a decent launch and not break something will be to leave at moderately high RPMs, hold the clutch at half engagement let it chatter a bit while the car gains a few mph then side step it. Either way I will be filming it all so it may be the shortest run ever if carnage ensues....

 

Yesterday was a complete bust. Was a 30% chance of rain in Tampa and Bradenton I left for the track yesterday afternoon. Its 65 miles round trip to track from my house. I got 5 miles from the track and it started pouring and the whole sky turned black. Turned around and drove another 90 minutes home in some of the worst rain ever. Luckily, I decided against driving to the track with the drag radials on. Weathermen don't know ****.

 

Stroker,

What is your primary inj. duty so high and secondary inversely so low? I'd want to dial the primaries back to get them around 80%, pumping more through the secondaries.

Have you played with leading/trailing split at all, swinging it a couple degrees each way to see if there is any change in AFR or EGT's?

Do you mind explaining the normality of the knock readings? That seems incredibly high, but I may be mis-interpreting the knock values from my experience tuning via piston engines like the SkyActiv 2.0 compared to a rotary.

EDIT: Likely already mentioned by someone else, but that RX-8 5spd center-section looks identical to the FD transmission (similar bell as well), major difference seems to be in the tail shaft assembly.

 

What is your primary inj. duty so high and secondary inversely so low? I'd want to dial the primaries back to get them around 80%, pumping more through the secondaries.

Adaptronics controls all of the injection duty cycling. It ramps up from P1 to P2 to Secondaries from 0-95%. They are all ID injectors that seem to have no problem handling the high duty cycle. Since I have been able to produce a relatively flat A/F curve, I see no need to make changes.

Have you played with leading/trailing split at all, swinging it a couple degrees each way to see if there is any change in AFR or EGT's?

I have tried different splits, I have found that I had the least audible knock(s) during tuning with a 12 degree split in the areas of highest load.

Do you mind explaining the normality of the knock readings? That seems incredibly high, but I may be mis-interpreting the knock values from my experience tuning via piston engines like the SkyActiv 2.0 compared to a rotary.

I have tuned my mustang without a knock sensor for more than a decade. It is right about 11:1 compression with up to 9 pounds of boost. I went through about 6 head gaskets on that motor which is still running. I have become an expert on lifting on audible knock. For the 13b motor, when I hear audible knock the values have been like 100-250 (when I chipped my apex seal racing I logged somewhere around 250). You can see a full blown backfire between shifts knock is hitting around 100. So when I see those 20-30 counts under full load with no audible knocking, breakup, or power loss, I am not worried at all. It is likely the knock sensor picking up the waste gate, maybe an exhaust leak, or some other engine noise.

EDIT: Likely already mentioned by someone else, but that RX-8 5spd center-section looks identical to the FD transmission (similar bell as well), major difference seems to be in the tail shaft assembly.

I have a FD transmission that came with my blown REW engine that is currently a backup to my rx8 5 speed. I will swap the bell-housing (rx8 push clutch vs FD pull clutch) and tail shaft when/if the time comes. I remember when people said I got ripped off buying a core REW engine with FD transmission for $1,350.00 shipped, now they are $3-4k on ebay all day long.

 

Ah okay -- I am not familiar with Adaptronics in the least, other than that they are quite popular with custom rotaries.

Okay, I guess the knock counts are more detailed in Adaptronics than I'm used to with the Sky-G tuning (Similar to Subaru logic) I've done. Usually knock events are binary, either it is knocking or it isn't, with knock significance measured in how many degrees of timing the ECU pulls. Sky-G method is to threshold knock constantly, trying to find the most efficient timing the engine will tolerate. They will slowly add in .25 degrees of timing until knock is identified, then it'll pull back .5-1* of timing for that cell where knock presented.

Eh, I'd say it is fair -- FD and FD parts pricing is retarded these days. My 94' was automatic, so I bought all of the parts to convert for around $1,300, keep in mind this was back in 2003/2004. The transmission, driveshaft, clutch+brake pedal, shifter, shift ****, stock flywheel, and a new ACT Street/Strip clutch was $800 all in, then I added a Racing Beat lightweight flywheel, new 5th gear synchro, new fluid, and some wiring odds and ends. $1,350 for a 'full assembly' of engine and trans (turbos, wiring, etc) seems good to me in the current climate.

Thank you for the added details, I've never done a calibration a rotary before, so I still have lots to learn.

 

I believe in a rx8 the knock sensor is little more than an engine stethoscope that converts engine loudness (certain frequency) into a number. In Adaptronics, you can set a base knock curve. So if in normal engine operation you get a normal knock count of 50, you can set your base knock to 50. So if you get a 50 knock count, it will actually show up in the log as "0". If you get a "75" knock count, it will show up as 25 (75 read-50 base). I have my base knock set real low so its very common to see 10-30 on my logs. I could set base knock higher so everything would read "0", but then I wouldn't have confirmation that the knock sensor was working. I do have a fail-safe that if I get over 50 knock that I retard ignition 5 degree's and enrichen fuel 10%. This however failed to save my motor when I chipped an apex seal. Even with a 250 knock event and a huge timing pull by Adaptronics the damage was already done. I may have been able to lift if I could have heard the knock event, but the damn mustang next to me was so freaking loud.

 

Update: Some more data.

40-100ish mph pull. Ambient temp was 83 degrees.

Duty Cycle is at 52 (3rd and 4th gear only), which was about 21 psi on this pull.

On this pull I was injecting about 1000 cc/min of 50/50 meth/water (2:1 into turbo compressor vs UIM).

Timing was conservative at 8-9 degree's total.

No significant knock under WOT

Intake Air Temp (IAT) at 107 F at start of run, and it 136 F just into 4th.

AFR was reading between 10.6-11.6 through the important parts of the run.



Even at 21 psi the car didn't feel as fast as the previous pull so I reviewed the logs to see what the data says.

On my previous 19 psi pull my delta x(RPM)/ delta t(time) was on average through 3rd gear at 732, which means I'm gaining 732 RPMs per second. From 0 to 8,000 RPMS the car will go from 0-100 mph (roughly) which means 1 mph per 80 RPMs.

I took the log data, specifically the delta x(RPM)/ delta t(time) (from 5,200-7,200 RPMs) in 3rd gear in all 3 logs and the data was as follows.

So for 17 psi - 686 RPMs per sec/80 = 8.56 mph/s acceleration
So for 19 psi - 732 RPMs per sec/80= 9.15 mph/s acceleration
So for 21 psi - 772 RPMs per sec/80 = 9.65 mph/s acceleration

Seems that I am seeing some slow down in acceleration per psi based on those calculation and maybe approaching the efficiency limit of the turbo. I would like to get a pull at 23 psi and see what the new data will tell me....

Then I got real bored and decided to plot those calculations on a graph with a logarithmic trendline to estimate what kind of turbo output I would need to increase my acceleration.

Here is the graph.



Based on the graph, I would need to upwards of 32-33 psi to get to 12 MPH/S in third gear. I know that this curve doesn't not take into account all the extra heat the turbo will make and the drop in efficiency (this estimate assumes linear efficiency drop), but its about as much as I can work with. I bet with more data points the line would begin to flatten out. Being that third gear on a perfect shift goes from 70-102, it would be nice to burn through the gear quickly.

This is the only way I could really think of determining whether I'm picking up or losing power on runs, anyone have any better methods they have in trying to interpolate the data?

 

Big event in Bradenton tomorrow night where I could get to blast down the 1/4-mile, so I took the car out to do some pulls.

I have used the exact same tune as before and developed some knocks. No rhyme or reason for it. Definitely audible and picked up perfectly on the knock sensor.

Still at 21 psi, A/F high 10s, Timing around 9 degrees total, 12 degree split. Water temp and intake manifold temps fine. Water/Methanol working as usual.

The only thing I think is that one of the leading coils is starting to go, which is not unreasonable since I already killed 5 of em.

I may just try to change the two front leading coils and change the spark plugs and see where that gets me. So frustrating that the car has been running great until tonight.

 

Update: Changed out leading coils on both rotors and swapped water/meth injection nozzles (1000cc/min in the Greddy Elbow, 500cc/min in turbo). Found that I blew a small vacuum cap off the manifold, not sure how that would cause knock. Took out 1 degree of timing and did a few more pulls.

Posted log below
40-115 mph, bouncing off rev limiter in 2nd and 3rd, let off halfway through 4th.
Turbo at 20 psi
No audible knock at WOT, not much in log either.
A/F around 11:1
Timing 9-10 total with 12 split
Manifold was heat-soaked at 120 degrees prior to pull. UIM temp 120-143 F
Ambient temp was 93
Was only gaining 8.5 mph/s in 3rd gear from which is the same acceleration I was getting at 17 psi on a previous pull. Power loss is likely because of the high ambient temps and heat-soaked intake manifold. Also down 1 degree of timing.
Looks like everything is back on track, but the heat here is unbearable.



.

 

Good news. They have a new E85 station only 6 miles from my home. I am getting ready to order my flex fuel sensor which I can wire into my Adaptronics Select.

I am looking for a good fuel calculator for a rotary to try and find out what my limit is on my injectors. I do not plan on running 100% E85. Just as a supplement (probably 50/50 at most) to get some more octane without some of the negative side effects.



Based on a log from yesterday on 93 octane with 19 psi on the turbo and 11.4:1 A/F, my car was essentially using 2,225 cc/min per rotor of 93 octane per rotor (4,450 cc/min total) plus roughly 450 cc/min of methanol total (225 cc/min each rotor). This leaves me approximately 500 cc/min left on each of the secondary injectors.

Lets say I mixed E85 and 93 to get a 30% ethanol content would that put me over my limit? If not, what kind of boost increase could I get before maxing them out?

Anyone know of a good ethanol mixing/injector sizing calculator for a rotary engine?

 

 

I already have a mount for a second Bosch 044 and could easily run a relay off of water injection pump (which comes on at 10 psi). I already have a second unused bung on the surge tank so no problem there.

Maybe the cheapest thing to do would be move the 1000 from Sec to P1 position. Buy two 1700 injectors and put them in the Sec position.

I would be going from 725/1000/1000 (2,725cc/min) to 1000/1000/1700 (3,700 cc/min).

An additional fuel pump and two injectors would cost about $750

I may just get the E85 sensor working first and add a few gallons of E85 in my tank and watch my duty cycles real closely then make the upgrade.

Edit: So I went to the gas station last night to verify that it did have E85 as I could only see from the road a special pump with the yellow marker on it. To my surprise it was only E20! ****!

 

 

 

 

 

Took the car out tonight for the first time in weeks, finally didn't rain here today.

Ambient temp 79 degrees
40-120 mph pull with turbo at 19 psi.
Spun through the top half of 2nd gear you can see the choppy RPM line which kills speed because I get into 3rd gear out of the power band.
A/F at 12:1 on tip in and ~11:1 once the turbo gets going
No discernible knock values (gold line)
Timing at 10-11 total, probably wont turn it up until fall and cooler weather.
Car is real smooth, hoping to get to the track once the rainy season ends....
Probably going to leave the fuel system alone for now as I need to get a baseline at this power level...

 

Well I think I am nearing the limit of what I can do on pump gas with water/methanol. Tired to add a degree or two at the top of the rev range to try and squeeze some more power out of this turbo and picked up a bit of knock at 6600 RPMs in 4th gear and let off (gold/brown line). The detonation started with the only cell above 22 psi in the log with leading timing between 8-10 degrees.

Ambient was like high 70s
30-115 mph pull with turbo at 20-22 psi.
Spun the tires up to 65+ mph in 2nd gear
A/F at 12:1 on tip in and ~10.7-11:1 once the turbo gets going
Timing at 10-11 total, gained some timing up top as the boost begins to drop off.
Manifold Temp went from about 115 to 145 on the pull

Its seems like no matter what I do, add boost, timing, or manipulate fuel, add/remove boost juice (even if no knocking detected), I just don't seem to be picking up any power. Seems like race fuel or a bigger turbo (or both) is my only option for more power.

 

When i went to E70 ... I went up 60HP at the same boost level without changing the timing at all. The EGT dropped about 20% as i remember. Worth a try if you have enough headroom on the injectors and pump. I guess this depends on if you can get E85 locally as well.

 

Well I went ahead and ordered my GM/Continental Flex Fuel Sensor (FFS), pigtail for FFS, -6AN/-6AN adapter for connection between return of FPR and FFS, both adapters for the FFS, and a 90 degree -6AN hose adapter from Amazon for $82. I hopefully will have this up and running by next weekend. I will just have to get some fuel cans and go get E85 from far away and mix it with my 93 octane.

Based on my last log at 7800 RPMs and 19 psi (turbo falls off above 7k) my secondary injectors are at 45%, which leaves me ~550cc/min injector left of the 1000cc/min secondary injector on each rotor.... I'm am using roughly 725+1000+450 (2,175 cc/min) max now.

If E85 uses roughly 40% more fuel, I would assume that E40-E45 requires 20% more fuel than 93 octane, E60 would require 30% more fuel than 93, etc....

2,175 cc/min x 1.2 (20% at E40) = 2,610 cc/min (I have 2,725 cc/min)
2,175 cc/min x 1.25 (25% at E50) = 2,719 cc/min (I have 2,725 cc/min)
2,175 cc/min x 1.3 (30% at E60) = 2,827 cc/min (I have 2,725 cc/min)

Based on these rough calculations, I would run out of fuel at 7,800 RPMs at 19 psi on E50 fuel. This would probably be okay since I shift around 7800-8200. I could either lower my rev limit or drop duty cycle on the turbo from 7,500 RPMs+. All of these calculations don't figure in the water/methanol injection. It should also be noted that all of these calculation have already figured in a max injector duty of 95% as shown in the logs and is not a true 100% max injector duty.

So it looks like I may make it there on the injectors with some small changes to the tune above 7,500 RPMs.

Will the single Bosch 044 be enough? Right now it holds 60 psi fuel pressure all the way to redline. Will it be able to keep up with a extra 20% of fuel be injected? We shall see..

 

 

Real Street Performance did a fuel pump test and reported that the Bosch 044 put out 436 lbs/hr of fuel at 60 psi (4 bar), which is 4,578 cc/min (same as your calculation). Looks like I will be at least 1,000 cc/min short on the fuel pump. Looks like I will be ordering another pump once I get flex fuel working.

 

New Update:

Flex fuel sensor installed. A Racetrack gas station opened up in August about 7 miles from my house.
On 93 octane I was getting a 15% ethanol reading in adaptronics. I thought 10% was the max in 93 octane so I'm not sure if the sensor is a bit off, minimum reading of the sensor is 15%, or I have some abnormally high E content in my 93 octane.
I mixed Klotz into the E85 and added about 2 gallons into the tank. Adaptronics gradually showed ethanol content increase from 15% to about 28%. It took about 5-10 minutes because the main tank had to mix and the surge tank had to mix before hitting the lines, rail, FPR, and sensor.
The content value seems about right since I had about 7 gallons of 93 mixed with 2 gallons of E85.





Yellow wire is MVSS and Green is Flex Fuel on CAS3

Adaptronics seems to be over-compensating for fuel which is making it super rich. Not sure if its the un-godly heat (ambient over 90), adaptronics over compensating, or the flex fuel sensor is reading a bit higher content that what it actually is....
Another weird anomaly is that when I got WOT, the flex fuel % drops which may be just be reduced flow over the sensor when all the injectors are opening...
Looks like I will be pulling fuel some fuel out of the E85 fuel compensation map and trying some more pull later on when it cools down. I'm keeping the revs low for now until I can monitor fuel pressure and secondary duty cycle.
Knock values looked good.