So, yeah... I guess this means people are reading the thread!
Something a good dynoguy/enginebuilder will sort out while making a ecu depending on a variety of different variables the engine at hand has
Not really, a good dyno guy might be able to smooth the curve, but that would just mean you're writing off power peaks as well as having a terribly inefficient intake. If your hardware isn't working, it isn't working and software can't fix that.
With ITBs you can really see the effect of inlet track on the torque curve, you'll see that an incorrect length causes the curve to take on a sinusoidal character as the engine responds to the harmonics of the inlet tract.
Exactly! Rama ran a simulation and I could see some of the effects he was talking about in that. We'll be testing a range of trumpet lengths for this reason.
I just went and looked at your other thread and read about the guy who posted those dbilas number's. I wouldn't put to much stock in them as they are very unscientific. He guessed on most of the variables! You really need to go to a real dyno and take a before and after run On that dyno the same day with the same/similar atmospheric conditions/temp's. And then if he showed a loss after that one would also need to know the things i posted above ^^. It is a good point though if the data is correct. Poorly set up ITBS will only Shift your power band with out gaining you bhp. They must be properly tuned with a properly set up plenum that is resonance tuned to the engine & proportionate to its flow characteristics .
-Tg
Yeah I'm not sure what the deal is with the dyno plots the guy was using - really weird.
A few thoughts though:
-I know for sure that the kink in the Dbilas manifold will have a significant negative effect on VE, from the simulations that I ran I know that for sure.
-Rama has convinced me that the ITB diameter is too large for the engine, so I am willing to believe for the moment that it at best won't help.
-Even if the absolute values are incorrect, the shape of the curve is terrible which does show it dropping power later in the curve
-Poorly setup ITBs won't just move the curve, they will lower the power and torque output
-So far as I can find, this is the
only dyno of the Dbilas ITBs, so as bad as it is it is at least something. At its best it indicates there is room for improvement, at its worst it indicates they are damaging engine output. From what I've learned doing this, I would be inclined towards the latter.
SNIP
The 'ideal' ITB set up is very extensive. You would have dual stage injectors, with one on the port side of the butterfly, and one on the intake side. You can generate significantly more power by injecting fuel further from the port, but this only works at WOT and high RPM otherwise the fuel won't get carried all the way into the engine and you can get a flame-out into the engine bay. You would place your ITBs with about 100~150mm distance from the valve to allow a smooth laminar transition into the valve profile.
This smooth transition is very very important, and it should highlight why I'm not keen on products like the dbilas ITBs. In the simulations I just posted up, a change in curvature that changed dimensions only a few mm results in a 1% reduction in efficiency. If you look at dbilas their kit has a sharp kink with no curved transition, which would have a very significant effect (I'd be willing to wager 10% or more) on reducing mass flow. You encounter the same issues when using an adapter plate. You would need to make an adapter plate 25~50mm thick to get an appropriate transition to maintain laminar flow - which would end up having defeated the purpose of putting the ITBs close to the port in the first place. It would be different if the butterfly was the same shape as the port, but it is circular and you need to accommodate that change in profile.
Hi there,
Im currently building (well since 5 years) my m42 with ITBs. I only used the dbillas intake flange as I preferred other brand itbs for personal reasons. The interesting thing is is that both the flange as the itbs have openings for injectors. I was planning on custom ecu to get ride of the barndoor air meter. This would allow me to use dual injectors per itb. One close to the butterfly and one close to the intake valves. Can you/anybody calculate (is that possible) from which starting point the programmer should start opening and closing each injector per rpm?
Im using catcams which open sooner and lift more
itbs are 45 mm
total lengt intake per itb is 250mm from intake port to cone trumpet
1st injector is at 10mm from intake port
2nd injector would be at 110mm distance
butterfly is at 120mm distance
Sorry man I can't help you with placing a second fuel rail. I only know the rules in the 'general' sense. What I know is that they are usually put on the intake side of the butterfly and not the port side, and they are usually placed one of the resonant lengths away from the valves for the RPM of interest. On the default unmodified M44 that is ~13inches from the port for ~5500~6500 RPM. The intake you have is too short for that anyway, so I doubt you would see any real improvement by implementing dual injection.
Which dbilas itbs did he use the standard or the race version? What kind of plenum did he use? Which injector set up? and what tuning? The only way i could see an across the board loss is if every thing was set up very poorly.
As I said earlier in the post - from everything I've learned so far, I would be inclined to believe that the Dbilas kit could institute an across the board loss. I can't confirm it, and I'm not pretending I know the answer definitively, but I would be inclined to believe that there would be very high vorticity in that manifold among other issues.
The most interesting item in that thread is the dyno chart where reducing ITB diameter for an M20 engine improved output across the board, but otherwise there is a lot more genuine interest and discussion here.
