Is there a build log anywhere for the SL-C?
- Thread starter epanarese
- Start date
It's exaggerated visually by the dual scale sheet. HP scale on the left and a different TQ scale on the right.
The biggest reason for the 20lbs of tq dips are overly rich fueling in that area. It goes to ~11.9:1 AFR in those dip areas (instead of 12.5-12.8:1). The dyno hours were adding up ($$) and I stopped chasing it that night and cleaned up those areas of the tune after leaving the dyno.
I think it made more than a .... *gasp* ... rotary :shocked::shocked::shocked::shocked:
:angel:
Dave: Here is a really quick video of it idling at 700rpm.
Haha... I think you should speak to Alex and go halves on having Fran install a Harwood snorkel scoop in place of the back glass. :laugh:
"The throttle crack tuning was tricky since it was dbw. If you cracked the butterflies an 1/8" and multiply that by 8 with the infinite plenum factor and the car launched from lights like a jackrabbit (unintended) until I took out loads of low speed timing,"
Same problem on fuel injected race bikes, the standard cure was about the same with tons of fuel right off the throttle stop. Makes it so fat for a split second it wont lurch off the corners. Kind of improtant on a RR bike with near 200HP! It also explains why you see long tails of flame coming off bikes on decel into corners. Fogarty's racebikes were famous for that.
Same problem on fuel injected race bikes, the standard cure was about the same with tons of fuel right off the throttle stop. Makes it so fat for a split second it wont lurch off the corners. Kind of improtant on a RR bike with near 200HP! It also explains why you see long tails of flame coming off bikes on decel into corners. Fogarty's racebikes were famous for that.
Seymour Snerd
Lifetime Supporter
Nice looking setup. Something about engines with ITB's makes me feel all warm and fuzzy.
:angel:
Running without any boost.
:angel:
Noooooo, come to the other side Doc ...... come to the twin throttle body side ... much easier to tune :idea:
You got me about power - theoretically it should I'd imagine (13'' runners, 3.13 cross section, etc...) but unless you did a back to back test on the same engine I don't think you could say for certain.
No, it's still gonna be more restrictive. ITBs should net you more power but as soon as you try to interrupt the airflow with filters, piping, etc. you cut into your gains. The more direct the route is to fresh air the better. You're better off running the ITBs into a plenum and designing a ram-air setup to keep that plenum full.
I wouldn't say sacrilegious. If you're running wide open throttle for an extended period of time you'll probably see less of a difference between the two setups. There's gonna be a big difference in throttle response though. You're going to have to fill those plenums with air before you can fill the cylinders with air, bit of lag time there. The cylinders are still sharing an access point to the air with the XR. ITBs should lessen the effects the cylinders have on one another. It depends how aggressive you want to get with your power delivery.
I guess we'll have to see on the dyno =)
But shouldn't the length of the runners (13'') and the massive plenum volume (15l) help give the twin 90mm tb setup an edge? I understand that the itbs will have a better throttle response, but what if he compare them in a street setup (i.e., itbs having some type of filtration so you don't suck down a rock)
Yes, once you put a filter on an ITB setup you lose a lot of your gains but ITBs still provide better delivery when comparing two filtered setups.
The problem with the manifold is that it's not just the size of the manifold that matters, it's how it flows. Tuning an intake manifold is more complicated than just slapping a big plenum on it. The runners are designed based on the powerband you're looking for. You also have to look at how the runners are connected to the plenum. This will play a big role in how the air flows from the plenum to the cylinder. For NA applications I believe it's generally better to get the mouth of the runner off of the wall of the plenum as seen on this Marcella manifold.
This becomes less important with a forced induction setup but when you're running an NA setup it's all about controlling the flow to get the best power out the engine. The more air you can bring into the plenum to feed the cylinders the better. However, putting the throttle body before the plenum makes this more problematic. You then have to size and shape the plenum to tune it to deliver enough air to each cylinder as it needs it once the throttle body is open. It's a simpler solution but there's a reason most high performance engines run ITBs (e.g. BMW M, Formula 1,...).
Here's a good little article about ITBs if you're interested.
ITB The Way It Should Be - Import Tuner Magazine
The problem with the manifold is that it's not just the size of the manifold that matters, it's how it flows. Tuning an intake manifold is more complicated than just slapping a big plenum on it. The runners are designed based on the powerband you're looking for. You also have to look at how the runners are connected to the plenum. This will play a big role in how the air flows from the plenum to the cylinder. For NA applications I believe it's generally better to get the mouth of the runner off of the wall of the plenum as seen on this Marcella manifold.
This becomes less important with a forced induction setup but when you're running an NA setup it's all about controlling the flow to get the best power out the engine. The more air you can bring into the plenum to feed the cylinders the better. However, putting the throttle body before the plenum makes this more problematic. You then have to size and shape the plenum to tune it to deliver enough air to each cylinder as it needs it once the throttle body is open. It's a simpler solution but there's a reason most high performance engines run ITBs (e.g. BMW M, Formula 1,...).
Here's a good little article about ITBs if you're interested.
ITB The Way It Should Be - Import Tuner Magazine
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