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NA injector upgrades
- Thread starter bngl3rt
- Start date
What other injector are you going to use?
RC Engineering is still using the older 80s technology injector.
The Injector Dynamic injectors are pencil spray patterned; probably not the best for the Honda port design (wider than tall).
RC Engineering is still using the older 80s technology injector.
The Injector Dynamic injectors are pencil spray patterned; probably not the best for the Honda port design (wider than tall).
I've heard of J-Series injectors being used successfully in C27A engines (G1 Legend, Accord V6 2.7)
only requiring OBD adaptor and a resistor modification to work.
There is a detailed DIY on the Legend forum.
Should work exactly the same in a NSX
obliviously not as good as K23A (RDX) turbo injectors but still a upgrade from the OBD-I injectors in older NSX's.
On a stock/mild NSX I'd stick with the RDX upgrade it's very cost effective.
only requiring OBD adaptor and a resistor modification to work.
There is a detailed DIY on the Legend forum.
Should work exactly the same in a NSX
obliviously not as good as K23A (RDX) turbo injectors but still a upgrade from the OBD-I injectors in older NSX's.
On a stock/mild NSX I'd stick with the RDX upgrade it's very cost effective.
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You’re going to see a gain if your new injectors mix the correct amount of fuel into the air better than your old injectors did.
An engine needs about 1 part of gasoline for every 14.7 parts of air for the mixture to burn properly. If you’ve floored the accelerator and the engine is spinning at 8000 rpm, you’re pumping as much air through the combustion chambers as you can. Your injectors need to flow enough fuel to keep up with that. If you inject even more fuel than your engine needs, you’re going to see a drop in horsepower after a certain point.
The higher the injector’s flow rate, the briefer the period of time it’ll need to be open to inject the proper amount of fuel. At full throttle, injectors with too high of a flow rate will be yawning with boredom and at idle, they may be open for so few milliseconds that they don’t atomize the fuel well anymore. If your engine isn’t inhaling enough air to need 440cc, 550cc, or 725cc injectors, installing bigger injectors isn’t going to get you a horsepower gain but it may mess up your idle.
Modern injectors can atomize fuel better and can have a better spray pattern than the OEM injectors in our engines, which are based on 1980’s technology. Better injectors can get you more horsepower even if they have the same flow rate as stock.
If you want to upgrade your injectors, you could try to figure out what flow rate you need and which injectors give you the best spray pattern and atomization. Honda installed 240cc injectors into NA1s with 270 hp. So Honda’s Formula 1 engineers felt that about 0.89cc’s per horsepower was enough for an NSX engine. Multiply your crank horsepower figure by 0.89 to see what minimum flow rate you should shoot for.
The next issue is spray pattern. Ideally, it would be good to have an injector that sprays fuel down the backs of the intake valves without wetting the walls of the intake ports. Given the geometry of an NSX’s cylinder head and the positioning of the injectors, each injector should ideally spray two cones of fuel (because there are two intake valves per cylinder) with a total spray width of about 30° to achieve that.
Then we come to atomization. Modern injectors with multiple holes in the spray nozzle can atomize fuel better than older single hole injectors do.
So what injectors give you the best flow rate, spray pattern, and atomization – irrespective of cost? Six 410cc RDX injectors flow enough fuel to support 460 crank hp in an NSX using the OEM NSX injector duty cycle. That’s more than any naturally-aspirated NSX using the stock intake manifold is likely to need. Their spray pattern is just about ideal given an NSX’s cylinder head and intake manifold geometry, they atomize the fuel well, and despite their size, seem to give a stable idle.
There may be an even better injector out there for naturally-aspirated NSXs with better atomization, a lower lag time, perhaps a lower flow rate, etc. If you hear about a better injector, whatever the price, please post about it.
An engine needs about 1 part of gasoline for every 14.7 parts of air for the mixture to burn properly. If you’ve floored the accelerator and the engine is spinning at 8000 rpm, you’re pumping as much air through the combustion chambers as you can. Your injectors need to flow enough fuel to keep up with that. If you inject even more fuel than your engine needs, you’re going to see a drop in horsepower after a certain point.
The higher the injector’s flow rate, the briefer the period of time it’ll need to be open to inject the proper amount of fuel. At full throttle, injectors with too high of a flow rate will be yawning with boredom and at idle, they may be open for so few milliseconds that they don’t atomize the fuel well anymore. If your engine isn’t inhaling enough air to need 440cc, 550cc, or 725cc injectors, installing bigger injectors isn’t going to get you a horsepower gain but it may mess up your idle.
Modern injectors can atomize fuel better and can have a better spray pattern than the OEM injectors in our engines, which are based on 1980’s technology. Better injectors can get you more horsepower even if they have the same flow rate as stock.
If you want to upgrade your injectors, you could try to figure out what flow rate you need and which injectors give you the best spray pattern and atomization. Honda installed 240cc injectors into NA1s with 270 hp. So Honda’s Formula 1 engineers felt that about 0.89cc’s per horsepower was enough for an NSX engine. Multiply your crank horsepower figure by 0.89 to see what minimum flow rate you should shoot for.
The next issue is spray pattern. Ideally, it would be good to have an injector that sprays fuel down the backs of the intake valves without wetting the walls of the intake ports. Given the geometry of an NSX’s cylinder head and the positioning of the injectors, each injector should ideally spray two cones of fuel (because there are two intake valves per cylinder) with a total spray width of about 30° to achieve that.
Then we come to atomization. Modern injectors with multiple holes in the spray nozzle can atomize fuel better than older single hole injectors do.
So what injectors give you the best flow rate, spray pattern, and atomization – irrespective of cost? Six 410cc RDX injectors flow enough fuel to support 460 crank hp in an NSX using the OEM NSX injector duty cycle. That’s more than any naturally-aspirated NSX using the stock intake manifold is likely to need. Their spray pattern is just about ideal given an NSX’s cylinder head and intake manifold geometry, they atomize the fuel well, and despite their size, seem to give a stable idle.
There may be an even better injector out there for naturally-aspirated NSXs with better atomization, a lower lag time, perhaps a lower flow rate, etc. If you hear about a better injector, whatever the price, please post about it.
I'm very curious to how a ID 725 would perform
If you want to provide me a set I'll be more than happy to dial them in and dyno test them at my next dyno tuning session.
It would be interesting to see if a J35 or J37 injector would be a better fit for NA from a flow rate perspective, assuming they use the latest nozzle design like the RDX K23.
I don't think the J-series injector would use the "newer" spray pattern; in Acura's press release for the RDX it specifically mentions the turbo motor necessitating a newer fuel injector design. I could be wrong.
I really don't think a bigger injector would perform better. As far as i understand RDX injectors will be more than good for any Tunned NA NSX (thinking about real world tuning).
What would be great is if a trusty company (like BOSCH, ID, RC...) could develope a line of injectors that had the correct spray pattern, and better atomization for the NSX, with flow rate begining on the 240 cc OEM and up. This would allow for a direct swap without needing to reprogrma the ECU for stock NSX's and bigger rate injectors for tunned NSX's...
What would be great is if a trusty company (like BOSCH, ID, RC...) could develope a line of injectors that had the correct spray pattern, and better atomization for the NSX, with flow rate begining on the 240 cc OEM and up. This would allow for a direct swap without needing to reprogrma the ECU for stock NSX's and bigger rate injectors for tunned NSX's...
I don't think a direct replacement injector, in terms of flow rate (240 cc/hr), is a good idea.
My experiments showed that the OEM maps are nowhere close to 14.7; I'm not sure how much to attribute to it but at the very least SOME of the power we made with the RDXs was due to getting the AFRs closer to ideal. Of course, the argument/conclusion can be made that the OEM 240s are nowhere near capable of supporting those ideal AFRs, especially on a lightly modded (I/H/E).
My car, at the time, just had Comptech headers.
I can’t believe Honda programmed the PGM-FI with an unsafe air/fuel ratio. NSXs are known to be pretty much bulletproof so I don’t think they left the factory running lean. At a dyno day in the UK, a bone stock 1997 Type-S and a completely stock 2003 NA2 were measured as running rich at full throttle.
Also, I do believe the OEM injectors can flow enough to support more horsepower than stock. My engine has intake, header, and exhaust modifications, intake manifold, cylinder head, and camshaft modifications, and it’s been running like that for 17 years with the OEM injectors. The engine management chip was reprogrammed on a dyno and the guy who did the programming never mentioned that the engine was running lean. He told me he kept increasing the pulse width of the injectors until power started falling off and then shortened the pulse width a touch again. In other words, at full throttle my engine is running as rich as it can while maximizing horsepower – with the stock injectors. Maybe the injectors now start spraying so early that at maximum rpm little pools of fuel collect on the back of the intake valves before they open (if so, then injectors with a higher flow rate would be good). I don’t know. But the OEM injectors can flow more fuel than they do in a stock engine.
If NSXs with the stock injectors and stock engine management chip run lean, I’d guess the PGM-FI can’t adjust the fuel trims enough to compensate for the increased airflow I/H/E modifications bring, the fuel filter is getting stopped up, the fuel pump is getting tired, or something like that.
Also, I do believe the OEM injectors can flow enough to support more horsepower than stock. My engine has intake, header, and exhaust modifications, intake manifold, cylinder head, and camshaft modifications, and it’s been running like that for 17 years with the OEM injectors. The engine management chip was reprogrammed on a dyno and the guy who did the programming never mentioned that the engine was running lean. He told me he kept increasing the pulse width of the injectors until power started falling off and then shortened the pulse width a touch again. In other words, at full throttle my engine is running as rich as it can while maximizing horsepower – with the stock injectors. Maybe the injectors now start spraying so early that at maximum rpm little pools of fuel collect on the back of the intake valves before they open (if so, then injectors with a higher flow rate would be good). I don’t know. But the OEM injectors can flow more fuel than they do in a stock engine.
If NSXs with the stock injectors and stock engine management chip run lean, I’d guess the PGM-FI can’t adjust the fuel trims enough to compensate for the increased airflow I/H/E modifications bring, the fuel filter is getting stopped up, the fuel pump is getting tired, or something like that.
In my experience with Honda C-Engines they tend to run rich.
I agree with greenberet on the fact bigger is not the answer efficiency is.
As far I know RDX has the best spray pattern second would be J-Serie and K-Serie.
Might be a interesting idea to check what the newest high efficiency engines from Honda do (economy engines).
They will be tuned for the ideal lean burn so atomisation is key although likely there flow/displacement will be too small
I agree with greenberet on the fact bigger is not the answer efficiency is.
As far I know RDX has the best spray pattern second would be J-Serie and K-Serie.
Might be a interesting idea to check what the newest high efficiency engines from Honda do (economy engines).
They will be tuned for the ideal lean burn so atomisation is key although likely there flow/displacement will be too small
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I agree. Injectors with a better spray pattern and better atomization will change the combustion process, which is what we want. However, if the combustion process has been changed, 240cc may no longer be the correct flow rate for a stock engine with the factory PGM-FI programming. Maybe injectors with a lower flow rate would be needed because the fuel is being burned more efficiently. Or maybe not. It would be great to test that and then sell the correct modern injectors to people who don’t want to put a new chip in the PGM-FI. I don’t know how likely it is that that’s going to happen, however.
Good point. Maybe Honda is installing injectors into some car nowadays that would work even better in an NSX than the RDX injectors do. Maybe Honda has a company tradition regarding the geometry of its four valve intake ports so that the injectors from one engine will have a spray pattern that works well in other Honda engines, too.
In any case, I’m looking forward to seeing how my engine likes Prospeed’s RDX injector kit. Regardless of the price, they're the best option I've found so far.
Did you order the Prospeed kit? Looking forward to your results!
As you are in Europe I also would be curious on your feedback on this injecors. Are you going to use Prospeed ECU tune, or will you have custom tune for your car (Using AEM engine management or equivalent)?
Yes, and it’s already arrived and is waiting to be installed.
Since I have high lift camshafts, ported cylinder heads, etc., an off-the-shelf tune isn’t going to work for me. I like the PGM-FI’s ability to learn short and long term fuel trims and its diagnostic abilities so I don’t want to lose that and install an aftermarket engine management system such as AEM. I’ve found someone local who can program a new chip for my PGM-FI while the car is on a dyno, so that’s the route I’m going to take.
hi guys!
I just was on the phone with my engine tuner and he said to me, that those HP gains are easly possible like Prospeed and others confirmed here. I think about on doing this mod too with AEM V2 which is already here.
Can you let me know who's the guy which modifiy your ECU? Is he in Austria?
PS: Please do a dynorun before the tune-up on the same dyno where you will run after the mod so we have a nice compare.
thanks!
I just was on the phone with my engine tuner and he said to me, that those HP gains are easly possible like Prospeed and others confirmed here. I think about on doing this mod too with AEM V2 which is already here.
Can you let me know who's the guy which modifiy your ECU? Is he in Austria?
PS: Please do a dynorun before the tune-up on the same dyno where you will run after the mod so we have a nice compare.
thanks!
There’s company called Chipfactory (www.chipfactory.at) just south of Vienna who have a dynamometer that they calibrate regularly (it was just recalibrated two days before I visited them), a clean workshop, and the people there made a competent impression. I brought them the OEM ECU from my PGM-FI, they were immediately able to read out the data and said yes, they can custom-program a chip like that for my NSX with the car on their dyno.
In addition to the RDX injectors, I’m going to have Comptech adjustable cam gears, a Power Enterprise Super Kevlar II timing belt, and an ATI crank pulley installed. Since I’m changing several things at once, a before/after comparison wouldn’t allow conclusions to be drawn about what impact the RDX injectors alone brought.
I’ll post up the results anyhow but what would be nice is to organize a dyno day including at least one bone stock NA1 five-speed as a baseline. Do you know of any around here?
In addition to the RDX injectors, I’m going to have Comptech adjustable cam gears, a Power Enterprise Super Kevlar II timing belt, and an ATI crank pulley installed. Since I’m changing several things at once, a before/after comparison wouldn’t allow conclusions to be drawn about what impact the RDX injectors alone brought.
I’ll post up the results anyhow but what would be nice is to organize a dyno day including at least one bone stock NA1 five-speed as a baseline. Do you know of any around here?
Do you have a shop where you let the cams adjust with the camgears? If not, I would recommend my engine tuner: Kaps Roman. If you like I can bring you into touch with him.
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Your guy will be able to adjust the cam gears with the engine still in the car?
I have been making plans to have my cams dialed in on an engine dyno (i.e., with the engine out of the car).
Let me know how it goes.
I’m in contact with two people regarding dialling in the camshafts, but thanks for the offer.
I don’t think the camshafts can be adjusted with the engine in the car so the engine will be coming out for the next service. Degreeing the camshafts on an engine dyno is an interesting idea. After speaking with Shad Huntley and Jon Martin I was just planning on retarding all four camshafts by 2° from the OEM specs if there is enough valve to piston clearance for that to favor top-end power over the midrange. Adjusting the intake and exhaust camshafts separately on an engine dyno to empirically tune the power curve to your personal preferences would surely yield even better results. I’d imagine the cost for that is extremely high, though. Have you looked into how many hours would be required to do that?
I don’t think the camshafts can be adjusted with the engine in the car so the engine will be coming out for the next service. Degreeing the camshafts on an engine dyno is an interesting idea. After speaking with Shad Huntley and Jon Martin I was just planning on retarding all four camshafts by 2° from the OEM specs if there is enough valve to piston clearance for that to favor top-end power over the midrange. Adjusting the intake and exhaust camshafts separately on an engine dyno to empirically tune the power curve to your personal preferences would surely yield even better results. I’d imagine the cost for that is extremely high, though. Have you looked into how many hours would be required to do that?
Dont't forget to insert the nwe LMA style when the engine is out.....at least if you still have the old style. *gg* ....I am very excited how much hp the mods will add. When do you think you will do all the mods? let us know!
They can be adjusted on the dyno. DAL Motorsports did this, then went to far on the dyno and destroyed an engine.
Hence, my previous thread inquiring about adopting VCT from the newer Honda's onto our old engine:
http://www.nsxprime.com/forum/showthread.php?t=152764
Gains on a boosted S2000 engine were impressive to say the least.
Dave
Hence, my previous thread inquiring about adopting VCT from the newer Honda's onto our old engine:
http://www.nsxprime.com/forum/showthread.php?t=152764
Gains on a boosted S2000 engine were impressive to say the least.
Dave
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