Ctsc

[jwmelvin]

Based on what I'm seeing from my car, if you are considering a Deatschwerks pump, consider the larger DW300. It's not that you need the higher overall flow, but at rpm with the stock CT fueling system, the DW200 cannot maintain 100+ psi. My AFRs are generally fine but climb a bit at high rpm and it seems to me the DW300 would be a better choice. Only a bit more expensive at ~$150 as compared with $100. There may be some disadvantage but I don't know of it. Of course, if you run piggyback or full EMS, then there would be no need for elevated fuel pressure and thus no need for such a large pump.

 

[Larry Bastanza]

How many miles on the car?

 

[jwmelvin]

How many miles on the car?

I figure you're asking the OP, but mine has 39k. :wink:

In seriousness though, it would interesting to hear your views on how the mileage changes things for a SC setup.

 

[NSXRAY1]

Based on what I'm seeing from my car, if you are considering a Deatschwerks pump, consider the larger DW300. It's not that you need the higher overall flow, but at rpm with the stock CT fueling system, the DW200 cannot maintain 100+ psi. My AFRs are generally fine but climb a bit at high rpm and it seems to me the DW300 would be a better choice. Only a bit more expensive at ~$150 as compared with $100. There may be some disadvantage but I don't know of it. Of course, if you run piggyback or full EMS, then there would be no need for elevated fuel pressure and thus no need for such a large pump.

I am still considering OEM vs AEM. The main thought is cost and how that all rolls together. For example, what is the total cost for additional parts for OEM. Versus the total cost for AEM and any additonal parts. Then the cost to install and tune or not tune. I will need to decide on Denso vs. other aftermarket fuel pumps as well. Lots to consider. Miay need to start a build thread?

My NSX has over 90k miles.

BTW DDozier or anyone, what would be the main reason to shy away from RDX injectors with a stand alone ECU?

Thanks

 

[DDozier]

[

BTW DDozier or anyone, what would be the main reason to shy away from RDX injectors with a stand alone ECU?

Thanks

With a standalone you can use any injector you want wthin reason. I would shy away from the RDX with the F/IC because of the high latency of the RDX injectors vompared to the stock injector latency.

Dave

 

[RYU]

[

With a standalone you can use any injector you want wthin reason. I would shy away from the RDX with the F/IC because of the high latency of the RDX injectors vompared to the stock injector latency.

Dave

Could that potentially cause a misfire upon throttle lift?

 

[DDozier]

Could that potentially cause a misfire upon throttle lift?

If you have no way to adjust the latency values within the ECU or your piggyback you will have some issues with the RDX injectors.

91-94 OEM Injector Info:
Size 240cc OHM 2 Latency ms 10v=.71 11v=.56 12v=.45 13v=.36 14v=.27 15v=.21

RDX
Size 410cc OHM 12.4 Latency ms 10v=1.8 12v=1.41 14v=1.1 16v=1.04

Other Injectors Info:
RC Engineering
Size 550cc OHM 3 Latency ms 10v=.92 11v=.81 12v=.68 13v=.59 14v=.51 15v=.40
Size 440cc OHM 13 Latency ms 10v=1.27 11v=1.08 12v=.91 13v=.74 14v=.63 15v=.53

Looking at the RDX injectors vs OEM there are going to be almost a full millisecond difference in latency, that is a very large difference in the world of injectors. This will effect the open and close time of the injector as the OEM ECu was calibrated for the much shorter latency of the OEM injector, with an RDX injector being controlled by a stock ECU your injector timing will be off with no way to correct it. In general when using larger injectors on a piggyback you want to use new injectors that act as close as possible to the injector you are removing to help eliminate latency issues. None of this is an issue on a stand-a-lone ECU as you will have the ability to adjust for latency.

Dave

 

[RYU]

If you have no way to adjust the latency values within the ECU or your piggyback you will have some issues with the RDX injectors.

91-94 OEM Injector Info:
Size 240cc OHM 2 Latency ms 10v=.71 11v=.56 12v=.45 13v=.36 14v=.27 15v=.21

RDX
Size 410cc OHM 12.4 Latency ms 10v=1.8 12v=1.41 14v=1.1 16v=1.04

Other Injectors Info:
RC Engineering
Size 550cc OHM 3 Latency ms 10v=.92 11v=.81 12v=.68 13v=.59 14v=.51 15v=.40
Size 440cc OHM 13 Latency ms 10v=1.27 11v=1.08 12v=.91 13v=.74 14v=.63 15v=.53

Looking at the RDX injectors vs OEM there are going to be almost a full millisecond difference in latency, that is a very large difference in the world of injectors. This will effect the open and close time of the injector as the OEM ECu was calibrated for the much shorter latency of the OEM injector, with an RDX injector being controlled by a stock ECU your injector timing will be off with no way to correct it. In general when using larger injectors on a piggyback you want to use new injectors that act as close as possible to the injector you are removing to help eliminate latency issues. None of this is an issue on a stand-a-lone ECU as you will have the ability to adjust for latency.

Dave

Thanks again for the awesome knowledge Dave. My piggyback has the ability to adjust for latency but we looked at this before and I'm questioning their values for the stock injector. I think you found them here? http://injector-rehab.com/shop/lag.html

Would you happen to have another source for this info? I'm not challenging your sources at all... I'm just hoping I find the right values to properly setup my baseline.

 

[DDozier]

Thanks again for the awesome knowledge Dave. My piggyback has the ability to adjust for latency but we looked at this before and I'm questioning their values for the stock injector. I think you found them here? http://injector-rehab.com/shop/lag.html

Would you happen to have another source for this info? I'm not challenging your sources at all... I'm just hoping I find the right values to properly setup my baseline.

We are sort of getting into the weeds here a bit on this thread but this is an issue with all piggybacks that do not take complete control of the fuel injector. I am not sure what your unit is doing but most look and measure the OEM ECUs pulse then add or subtract from that pulse time to add or remove fuel. Yours may not work that way but the F/IC does. This presents a problem as the OEM ECU calculates the pulse width for an injector by looking up a fuel map and adding in the injector latency or dead time to determine when and how long to fire the injector. The WHEN is the important part, if the injector is slower to open and close then the original and the ECU does not know that, then the Injector will not open early enough and will close later as well causing fuel to remain on the back of the valve after it has closed. It will be not be used the next time the valve opens and that will throw off your AFRs as well as cause a few other problems. It will run the engine but you will have a few weird other issues associated with injector timing that will show up in drivability issues and trim issues. It does not always effect every car and the larger the injector and larger the variation in injector latency the more likely you will have a problem. The last car I setup with the RDX injectors and I did not have the ability to correct for the longer latency would run and drive fine unless the engine was in a steady state for a long time, cruise for 20 min at about the same throttle and load and the long term trims would start to move a long way from were they should be. If you correct for the trims using the offset fuel map then go into that same cruise state and the trims would move the other way. I finally gave up and put in different brand of injectors and the problem was not there. May have been an anomaly but injector latency is the only thing that made since to me. Even in the F/IC you can correct for the latency somewhat but there seems to be a limit to how far you can go.

If you can not change this value and you change the injectors to something completely non-similar to the original injector then you have to play with the fuel table and try and get it right. If your piggy back is running the injector entirely and is ignoring the ECU then you will not have any issues as long as you give the piggy back the correct injector information.

Latency numbers in general are kind of all over the place, but those are similar to what I have found in other places. In general low impedance injectors are much quicker than high impedance injectors and the OEM units are low impedance while the RDX are high impedance, but even given that the RDX injector is one of the slowest injectors I have ever seen, it can cause issues if you are running them at higher duty cycles. Due to their high latency there is a finite length of time the injector has to open and close while the intake valve is starting to open and is then closed, I have not done the math but at 8000 RPMs and high loads the RDX at high duty cycles may be to slow. I would love to know if this is truly the answer as it is all speculation on my part and I do not have the time to research the issue.

That is really all I can add about them and without knowing you particular piggyback I am guessing you may be battling some of the same issues that I had with the RDX injectors.

Dave

 

[RYU]

Thanks again Dave. Maybe I should email you but i'm also hoping this information will helpful for other people also. I know this is perhaps not the right place and we're indeed getting into the weeds. If you have some more spare time perhaps you can give me some ideas of what area of the tune to look into given the info below.

I'm using the HKS F-Con iS which is their OBD1/OBD2 Piggyback computer on my 1991 NSX. I know that very few people are familiar with this unit unfortunately. It's a little more sophisticated than an F/IC but it's still a piggyback. It's now tuned to run pretty darn well on the RDX injectors. Cold start is good. It maintains 14.7 AFR in closed loop and it's setup to run a little rich at open loop (WOT) so Open and Closed loop has been pretty good. In general throttle tip-in is like stock BUT I do have two issues which is becoming bothersome.

1. At anything greater than ~70-100% throttle and upon a quick deceleration or depress of the gas pedal the car will misfire and jerk around for a split second. It almost feels like the fuel pump is cavitating and the car runs out of gas. The sympton is directly correlated with how fast I let go of the gas pedal. If I decelerate gradually there are no issues. If I decelerate abruptly then the engine misfires on decelerations. It seems like the abrupt throttle body closing causes come kind of surge and remaining fuel is burnt off incorrectly. That's what leads me to believe I might have a injector latency/dead time issue and i'm simply compensating for it with the fuel trims elsewhere in the tune. I'm not really sure this is the case since we've tried a few settings on the latency/dead time compensation in the HKS piggyback. I never had this issue with the factory comptech fueling stuff. The issue I had with the Comptech was some hesitation at WOT during the VTEC crossover point and it's overcompensation for high IATs - both of these are off-topic here.

2. Does the OEM ECU have a barometric correction? One of the reasons I went with a piggyback was to use the factory ECU's altitude compensation tables. It doesn't seem like there's any correction for altitude at all. When i'm at 3000+ ft and higher it's running rich rich rich. Thoughts?

 

[jwmelvin]

Just a request that you keep the conversation here as this is all very helpfully informative for the rest of us. I am moving my CTSC system to an AEM FIC, so while the specifics of your F-Con will not apply, many other aspects might.

I believe the OEM ECU does have a barometric correction, which is always applied. See this post.

 

[DDozier]

Thanks again Dave. Maybe I should email you but i'm also hoping this information will helpful for other people also. I know this is perhaps not the right place and we're indeed getting into the weeds. If you have some more spare time perhaps you can give me some ideas of what area of the tune to look into given the info below.

I'm using the HKS F-Con iS which is their OBD1/OBD2 Piggyback computer on my 1991 NSX. I know that very few people are familiar with this unit unfortunately. It's a little more sophisticated than an F/IC but it's still a piggyback. It's now tuned to run pretty darn well on the RDX injectors. Cold start is good. It maintains 14.7 AFR in closed loop and it's setup to run a little rich at open loop (WOT) so Open and Closed loop has been pretty good. In general throttle tip-in is like stock BUT I do have two issues which is becoming bothersome.

1. At anything greater than ~70-100% throttle and upon a quick deceleration or depress of the gas pedal the car will misfire and jerk around for a split second. It almost feels like the fuel pump is cavitating and the car runs out of gas. The sympton is directly correlated with how fast I let go of the gas pedal. If I decelerate gradually there are no issues. If I decelerate abruptly then the engine misfires on decelerations. It seems like the abrupt throttle body closing causes come kind of surge and remaining fuel is burnt off incorrectly. That's what leads me to believe I might have a injector latency/dead time issue and i'm simply compensating for it with the fuel trims elsewhere in the tune. I'm not really sure this is the case since we've tried a few settings on the latency/dead time compensation in the HKS piggyback. I never had this issue with the factory comptech fueling stuff. The issue I had with the Comptech was some hesitation at WOT during the VTEC crossover point and it's overcompensation for high IATs - both of these are off-topic here.

2. Does the OEM ECU have a barometric correction? One of the reasons I went with a piggyback was to use the factory ECU's altitude compensation tables. It doesn't seem like there's any correction for altitude at all. When i'm at 3000+ ft and higher it's running rich rich rich. Thoughts?

1. The OEM ECU should be doing a complete fuel cut when its sees a large change in throttle position. You should be able to log AFR and TPS and see how fast that transition is. If the car goes rich or stays in the 15:1 area before going 20:1 then you are not getting a good fuel cut. Without knowing your piggyback there may be something it is doing to cause this as well. You could also be having a latency issue but I really do not know what to tell you, other than to try throwing in another set of injectors but you will have to redo your tune.

2. I have to go back and check the code but from my memory I think the OEM ECU samples the MAP sensor at key on before the engine starts and that is what it uses as its Baro reading. I could be wrong and there may even be a BARO sensor on the ECU main circuit board. Either way it does have a BARO correction that is calculated into the fuel trims. One thing you can try for the fun of it is start the car and drive to a higher elevation, do not shut off the car and monitor your trims and AFR at WOT. Shut the car off for a few min. then start the car and check everything again and see if the BARO adjusted on restart. If it did then the OEM ECU is only sampling the BARO at startup. Keep in mind the BARO trims values are based on small 240cc injectors and a 5% change on a 240cc is about half of a 5% change on a 410cc injector so all the trims are going to be exaggerated. I am guessing at how much the BARO trim really is but the idea is there. Non of this should mater in closed loop other than your trims will move around, but in open loop you should see a change.

Dave

 

[NSXRAY1]

Dave, thanks very much for all of the great information. I have finally made a decision on moving toward an AEM EMS. I see the figures you listed for the injectors. Since my knowledge on this topic is very limited, I am thinking of staying away from the RDX injectors and contemplating 440 or 550 injectors. More to come with this build. Keep the information and suggestions coming in on this thread it is plenty helpful. Too bad I am not in St. Louis I would really lean on you for help.

NSX Prime is a great place. :smile:

 

[jwmelvin]

With a standalone, you have no reason to avoid RDX injectors as I understand it. If the size is adequate they seem good for a standalone.

 

[NSXRAY1]

With a standalone, you have no reason to avoid RDX injectors as I understand it. If the size is adequate they seem good for a standalone.

Thanks for the tip. However, I am a little confused because Dave had recommend to use larger injectors. Do RDX injectors come in larger sizes than 410?

 

[jwmelvin]

No, that's the size. If they will flow enough for you then they will work. You can raise the fuel pressure some to help them. Supposedly they like ~10 psi more than the stock injectors, for better atomization. Especially if you are sticking with the low-boost pulley then they should be fine. RYU is using them in such a setup.

 

[NSXRAY1]

No, that's the size. If they will flow enough for you then they will work. You can raise the fuel pressure some to help them. Supposedly they like ~10 psi more than the stock injectors, for better atomization. Especially if you are sticking with the low-boost pulley then they should be fine. RYU is using them in such a setup.

Good to know. I thought I was tied to only going with any other high output injecter other than the RDX. Keeps the idea of multiple options open. Thanks

 

[NSXRAY1]

Hello Prime,

I have all my CTSC parts and planning for the installation. I have contacted a couple of installation shops for quotes. One of the shops asked if I had changed my clutch. I have not changed the clutch and was not planning to change the clutch because I am planning to only push the car to about 350hp.

Quick question. I currently have the OEM clutch and it is in good operating condition.

Should the OEM clutch be replaced?

Thanks

 

[Hagasan]

Hello Prime,

I have all my CTSC parts and planning for the installation. I have contacted a couple of installation shops for quotes. One of the shops asked if I had changed my clutch. I have not changed the clutch and was not planning to change the clutch because I am planning to only push the car to about 350hp.

Quick question. I currently have the OEM clutch and it is in good operating condition.

Should the OEM clutch be replaced?

Thanks

I fitted my CTSC back in April and got about 387hp on the dyno. I'm using my OEM clutch which had maybe 10k miles on it at the time of SC installation. So far I've had no issues at all but I don't do racing starts.. I think if your clutch is in good health currently and you drive "considerately" you should be fine. I'd say try the car as it is once your SC if installed... Then just replace the clutch if you run into problems and need too...

 

[NetViper]

Hello Prime,

I have all my CTSC parts and planning for the installation. I have contacted a couple of installation shops for quotes. One of the shops asked if I had changed my clutch. I have not changed the clutch and was not planning to change the clutch because I am planning to only push the car to about 350hp.

Quick question. I currently have the OEM clutch and it is in good operating condition.

Should the OEM clutch be replaced?

Thanks

I have been running the oem clutch for a few years with no issues. I'd leave it. Replace it only when you need to.

 

[kingtal0n]

I Personally do not like the idea of 100+ PSI of fuel pressure, it really is a "band-aid" as he put it. What about ignition timing? You might hit the A/F target but how are you pulling out boost timing? Sounds like the ECU will be locked at WOT timing for the naturally aspirated engine.

I am surprised nobody plays with Air-Flow converters (SAFC) instead. It would accomplish the same "band-aid" without the increase in fuel pressure. Again, there is the issue with timing.

edit: I just noticed some of you are using air flow converters (HKS F-con). And the symptoms you describe are typical. It is just a temporary solution to the age old problem of tuning, and a piggyback, no matter how well designed, is going to butt heads with the OEM ecu at some point and you may feel it.

 

[Cody@LoveFab]

http://www.nsxprime.com/forum/showt...-Drive-By-Wire-AEM-Infinity-Management-System.

Check out our new system. Seamless drivability and unparalleled safety margins. While a little costly, its a lot less expensive than a blown motor.