Hello Folks. With the help of Spoolinup, I've made the switch from Prius/Yaris coils to R35 GTR coils. R35 GTR coils (which I'll just call "GTR coils" for the remainder of this post) are known to produce excellent spark energy. PRP says that spark energy is ~50 mJ and duration is a bit more than 2 ms. These are both excellent values. In comparison, Prius/Yaris coils produce around 30 mJ and less than 2 ms spark duration.

Getting GTR coils to work on an Evo is not quite as easy as Prius/Yaris coils for two reasons. First is that the boot length is too short to have sufficient overlap on the spark plug ceramic, and when attempting to use GTR boots, there is a good chance that there will be spark energy leakage down the ceramic insulator. In my case, spark energy leakage with the GTR boots was substantial enough that I had spark blow out at less than 15 psi with a spark plug gap of 0.028 inches. The resolution to this issue is to use a longer coil boot that Spoolinup includes as part of his GTR coil COP kit.

The other issue is that GTR coils have a very low primary winding resistance, and if the harness supplying power to the coils has any non-trivial amount of resistance, the primary winding voltage drops very low during coil charging, and spark energy is reduced. An example of this phenomenon is shown in Figure 1 that shows primary winding voltage as a function of time during coil charging using the factory Evo coil power harness. The primary winding voltage at peak charge with the factory coil power harness is only 9.3 V which is pretty poor. The goal is for the primary winding voltage to not drop at all during charging, so ideally it should be ~14 V at saturation. It is pretty tough to get no voltage drop in the primary winding during coil charging, but thanks to Spoolinup, I now have a custom power harness that gives 13.4 V at saturation as shown in Figure 2.



Figure 1. Coil primary winding voltage versus time for GTR coils using stock Evo coil power harness.



Figure 2. Coil primary winding voltage versus time for GTR coils using Spoolinup coil power harness.


Another issue with using the factory coil power supply harness is that the low voltage at the coils lengthens the time for the GTR coils to reach full charge. As can be seen in Figure 1, even at 4.25 ms of dwell (charge) time on the factory Evo coil power harness, a GTR coil still hasn't reached saturation. If you're like me and have a (crappy) oscilloscope where the dwell time to full charge can be observed and then input into the ECUFlash coil dwell settings, its ok if time to saturation is very long. However, if you're the average person who is going to use stock Evo coil dwell values or use values published on the internet that are based on GTR coils seeing 14 V, using the factory harness is going to result in very low spark energy. I'd venture to say that using the GTR coils with the factory Evo coil power harness and factory dwell settings will result in lower spark energy than running Prius/Yaris coils with the factory Evo coil power harness and dwell settings. This is because the Prius/Yaris coils have a higher primary winding resistance, and primary winding saturation is obtained at dwell values not too different than the factory Evo dwell time settings. Bottom line here is that GTR coils are a waste of money when used with the factory Evo coil power harness. Spoolinup will only be offering GTR coils with his custom coil power harness. Its dead simple to install, so don't be worried about any extra complications when using his harness.

Figure 3 shows a photo of the coils installed on my Evo. This is an early version of this configuration, so there are some extra holes in the mounting plate, and the wiring configuration is not optimized, but this shows the likely final clocking of the coils that allows the COP kit to be 100% plug-n-play. I'm talking with Spoolinup about a few more tweaks that may allow the GTR coils to fit under the factory coil cover plate.



Figure 3. GTR coils installed on my Evo.

Figure 4 shows my coil dwell time tables for the GTR coils with the Spoolinup GTR coil power harness. As I said earlier in this post, these dwell times are way too short for GTR coils on the factory Evo coil power harness. If you don't have these tables defined in your ROM, please see my coil dwell time disassembly thread in the ECUFlash forum.



Figure 4. ECUFlash dwell values for GTR coils with Spoolinup coil power harness.

I'm using the GTR coils in combination with an NGK DILFR7B10G spark plug that is the same design as the factory GTR spark plug except that it fits in an Evo and is heat range 7. An image of the tip is shown in Figure 5. The electrode and electrode ceramic look identical to the factory Evo 9 NGK ILFR7H spark plug. The difference is the use of an iridium tip on the ground strap. I have these gapped to 0.8 mm (0.0315") which is factory GTR spec. Compared to the Prius/Yaris coils that came before these, the GTR coils with these spark plugs provide more stable warmup, a more stable idle, and more off-boost pep. I think its quite reasonable to assume that the stronger spark energy is doing a better job of fully igniting lean mixtures typical of off-boost driving. As far as WOT power goes, I think the prevailing notion for coils and plugs is that as long as there is no spark blow out, a stronger spark has minimal effect on power. I think that is roughly true for the upgrade from Prius/Yaris coils to the GTR coils, but I feel very confident in saying that this combination of coils, plugs, and spark plug gap on my Evo (550 whp, E85) makes the car more responsive to throttle input and have a bit more pep when on-boost. Overall, I think they are well worth it for the improvement in off-boost performance alone. Judging by how well these do on my moderately powered Evo, I think these are going to be the go-to coil for high power builds.



Figure 5. NGK DILFR7B10G spark plug tip that is compatible with an Evo 9.

 

Nice write up !!

 

Outstanding Work!!!!

 

Mr Fred does it again !! great job ....:-)

 

Good job and write up. I believe there was no R35 coil measuring numbers around on the internet.


-Another reason as to why there is a certain delay and voltage drop during power up the primary winding, is not only the bottle necks of the stock evo harness, it is also down to the type of capacitors and transistors and their circuitry of the stock ecu. The ecu is made to work well with the stock evo coil system and its capabilities. One using an aftermarket ecu, such as motec, link, hatech, hks etc on the right dwell times, will observe that this problem does not occur even with the stock harness.


-Also not all toyota coils are the same. They vary between 35-45 mj. The toyota coils for V8 4.7L engines such as lexus / tundra / sequoia have more spark energy to the plug, around the 40-45 mj mark. This is more than enough for a 1000+ hp setup, especially on aftermarket ecus. Cheaper than R35 coils also.

-I have tried both type of coil r35 and the toyota 4.7L coil. I have experienced no difference in performance on my setup. Custom self made harness,aftermarket ecu.



-It is definitely worth getting a ready made spooling up kit though, instead of the more expensive capacitive discharge systems.


-It is always better to have a coil that needs lower dwell times, and also not close to its saturation point.


-R35 coil has around 200mj primary winding energy I believe, which puts it among the highest, if not the highest performing oem inductive coil on the market.


- A misconseption that goes around is that, the spark blows out, the spark does not blow out, what actually happens, is for the spark to have difficulty to jump and or be very weak.


Hat's off to you my friend for your contribution to the evo community.





Marios

 

Great write up, thank you for another awesome contribution to the community. I've been cobbling together parts to do a GTR coil setup also, and I appreciate the research you put in to testing the electrical characteristics of this setup.

I thought it might be good to point out for anyone interested that if you will be installing a relay to power these things, it is as good as an opportunity as you will get to also install a kill switch.

All the ECU is doing is sending a high impedance active low signal to trigger the coils. As long as your upgrading the power supply to the coils the ECU shouldn't matter as falling edge is typically pretty fast. AFAIK as long as the proper dwell times are programmed it shouldn't make a difference. I mean if you wanna contribute some scope captures to prove your point then by all means. OP started this thread to talk about GTR coils, If you want to talk about tundra coils I think it would be more respectful to OP if you started your own thread about that.

 

Thanks. I haven't tinkered with my Evo in a while, and it was a fun project.

As Biggiesacks said, all I did on the power harness was switch the coil power source (and ground). No part of the coil power supply goes through the ECU. I didn't post it here, but I've also done current draw measurements on the primary winding of the GTR coils, and they pull 14 amps as they reach saturation on the Spoolinup harness. That kind of current will not be going through the ECU. This reminds me that I forgot to mention in my original post that since the Evo is a wasted spark setup where two coils are charged simultaneously, peak draw is going to be 28 amps on the Spoolinup harness.

Interesting info on the Toyota coils. Do you know the PNs for the higher output versions?

ok on the "blowout" terminology. I understand what is actually happening, but decided to use the more typical word description.

 

Excellent work Sir. You've contributed so much to this community over the years. Thank you.

If you end up back on the dyno at some point and want to test the toyota vs gtr coils you should be able to use smoothing 0 and see the clear difference.

I can agree with Marios on aftermarket ecu's effect on ignition strength . Also an aftermarket ecu's native language is speed density. You can filter the map signal so that also makes the car run better/cleaner.

Any other changes in the pipeline this year?

 

I'd be happy to be proven wrong here, but I don't see how that's possible considering the circuit that powers the coils is completely isolated from the ECU. I mean if we are talking stock ECU with untuned dwell times vs. aftermarket ecu with dialed in dwell times then sure. Maybe there is something at play that I am missing here?

 

Thanks. Several other items planned if I can find the time. Top item is finishing a better SD implementation. Next is that I have a ported Skunk2 IM that I will eventually try. Finally, I may switch back to S2 cams. I have R2s working great, but the S2s will lower the boost threshold by at least 300 rpm, and that's worth it to me, especially if I can gain some top end with a lower restriction intake that will go with SD.

Perhaps what's happening here is that some people with aftermarket ECUs are not using wasted spark. This would would halve the current draw.

 

That....makes perfect sense. Thank you for the enlightenment. Mario's, Abacus my apologies. I should have asked more questions instead of trying to dismiss what you were saying.

 

No you are wrong, and I am by no means trying to create any negative conditions, it is not a just a matter of having the right trigger type for the coil to break the magnetic force-field and feed the plug, i.e a rising edge or falling edge trigger. It is the ecu who is creating the forcefield and the ecu which breaks it. An ecu capacitor , transistor and driver has certain capabilites and limits in storing and trasmiting voltage, in other words how fast, strong and consistent. It is the ecu which charges the coil, it is the ecu driver that controls the coil. The same effect goes for a weak harness , of the wrong gauge, the wrong route, the wrong parts used, resistance issues etc. Aftermarket ecus have parts of higher capabilities. For instance I run a power fc Pro, and the dwell times for stock coils are different than the ones on the stock ecu.



This is a thread about coil packs, and its here to help evo owners, it might be about the r35 coil pack, but mentioning another type of coil pack as comparison part to the r35 coils, and as an alternative to them, is also a helpful part of the conversation, and it does fall very much in the spectrum of respect. If the O.P has a problem with my tundra mentioning part he can ask me to remove it. It would have been dis-respectful if I did not accept the above findings, considered biased or false, and objected to it, by providing findings on the Lexus coils on this thread. I do know how the r35 coils perform as I have used them, hence why I agree with his findings. I merely gave to others and to the O.P some more food for thought on the matter in case that interests them.

Here is a link to the ones I am talking about :https://www.holley.com/products/igni...n/parts/822183



Again if my posts are not welcome by the O.P, I will remove them no worries at all.






Marios

 

There is an off-the-shelf kit out there for R35 coils on an Evo: https://jdcustomsusa.com/products/jd...1000hp-non-cdi

And some testing on various coils here:

 

Just watched the video, the only thing that I disagree on is the fact of running the coil near close to its saturation point. It will give the best outcome, but through the constant amount of usage , i.e running the setup at full boost for half an hour the coil will overheat. I also found the yaris bosch coil to be at 40mj back in the day. Even at 35mj is enough to run 1000hp. It goes without saying that running the r35 coil pack one can do 1200hp.







Marios

 

- I was referring to the signal/trigger part.


- I've put a link above in regards to specific coils.







Marios