Big cams, OE manifold, way down on power.
Discussion
227bhp said:
That is the reason for the thread yet two experienced people think a cam will help me and others have also reported +25 - 30 more than I currently have with this manifold on a similar engine.
at some people you have to make a change and see what happens for yourself. i think a smaller exh cam will help immensely but not necessarily at the topendEdited by 227bhp on Wednesday 15th January 15:04
what brand and P/N cam is it? catcams based on the 0.1mm duration reference?
Inline__engine said:
ITB help at idle and part throttle when the blade is partially closed. At WOT itb are not going to help reversion and driveability it will behave the identically to a single throttle engine with same runner geometry except for a tiny bit of restriction
The point I am getting at is why?If MAP is being used as the load reference for the ECU, then you can run into problems which worsen low speed operation. The ECU sample rate of the MAP sensor is fixed. The MAP is not for a given engine speed. You get pulses of MAP depression as each cylinder goes through the intake stroke, thereofor the MAP the ECU sees is not representative of true cylinder filling.
I have logged MAP on my engine and at low engine speed I can clearly see the MAP oscillating in time with rpm. Only when the rpm rises above the ECU sample rate does the MAP reading smooth out.
Likewise with MAF and long cams, the reversion pulses oscillate up and down the intake tract. The same air can pass the MAF sensor more than once. The ECU thinks there is more air entering the cylinders than actually is.
This is the same for plenum intakes and ITBs.
Changing to ITBs appears to help as it is normally done in conjunction with a swap the A/N (TPS/RPM), where TPS is the load reference. If you can't accurately measure the air entering the engine, then don't. Create a map based on the TPS as load.
No answer yet as to ECU type or load ref.
It may be using a torque demand map, where throttle opening (DBW), inj PW, Inj timing and ignition timing are calculated to deliver the torque demanded. In this instance, the quantity of air entering the engine must be measured, or referred to an VE model in the ECU and corrected against measured data, one channel being mass air flow.
stevesingo said:
The point I am getting at is why?
If MAP is being used as the load reference for the ECU, then you can run into problems which worsen low speed operation. The ECU sample rate of the MAP sensor is fixed. The MAP is not for a given engine speed. You get pulses of MAP depression as each cylinder goes through the intake stroke, thereofor the MAP the ECU sees is not representative of true cylinder filling.
I have logged MAP on my engine and at low engine speed I can clearly see the MAP oscillating in time with rpm. Only when the rpm rises above the ECU sample rate does the MAP reading smooth out.
Likewise with MAF and long cams, the reversion pulses oscillate up and down the intake tract. The same air can pass the MAF sensor more than once. The ECU thinks there is more air entering the cylinders than actually is.
This is the same for plenum intakes and ITBs.
Changing to ITBs appears to help as it is normally done in conjunction with a swap the A/N (TPS/RPM), where TPS is the load reference. If you can't accurately measure the air entering the engine, then don't. Create a map based on the TPS as load.
No answer yet as to ECU type or load ref.
It may be using a torque demand map, where throttle opening (DBW), inj PW, Inj timing and ignition timing are calculated to deliver the torque demanded. In this instance, the quantity of air entering the engine must be measured, or referred to an VE model in the ECU and corrected against measured data, one channel being mass air flow.
it seems like you are more talking about the load sensor strategy If MAP is being used as the load reference for the ECU, then you can run into problems which worsen low speed operation. The ECU sample rate of the MAP sensor is fixed. The MAP is not for a given engine speed. You get pulses of MAP depression as each cylinder goes through the intake stroke, thereofor the MAP the ECU sees is not representative of true cylinder filling.
I have logged MAP on my engine and at low engine speed I can clearly see the MAP oscillating in time with rpm. Only when the rpm rises above the ECU sample rate does the MAP reading smooth out.
Likewise with MAF and long cams, the reversion pulses oscillate up and down the intake tract. The same air can pass the MAF sensor more than once. The ECU thinks there is more air entering the cylinders than actually is.
This is the same for plenum intakes and ITBs.
Changing to ITBs appears to help as it is normally done in conjunction with a swap the A/N (TPS/RPM), where TPS is the load reference. If you can't accurately measure the air entering the engine, then don't. Create a map based on the TPS as load.
No answer yet as to ECU type or load ref.
It may be using a torque demand map, where throttle opening (DBW), inj PW, Inj timing and ignition timing are calculated to deliver the torque demanded. In this instance, the quantity of air entering the engine must be measured, or referred to an VE model in the ECU and corrected against measured data, one channel being mass air flow.
at idle part throttle the blade helps stop the reversion by physically blocking waves (partially) and helps to isolate each runner from each other when a common air box is used. When you go WOT the blade doesn't stop reversion anymore and with a mild volume airbox there is still some communication across runners so its no different o most other common box setups. A true IR has infinite volume airbox so the runners dont cross talk unless you run a small manifold log for idle control or map signal
MAP for primary load sources on ITB is not the best unless the ECU can sample at a specified crank angle to capture the meaningful part of the signal. That's why most use Alpha N as an aftermarket ECU is often getting fitted which doesn't have the proper sampling capability for the job. You can sample from all runners to a common small plenum but the resolution of the signal is pretty poor IMO (can stop pulsing for the most part with appropriate small restrictor) such that Alpha N just works better anyway and better again with a MAP correction. Similarity reversion can make a MAF confused but when you talk race cams and ITB a MAF is not normally used. BMW used an Alpha-N with MAP correction system iirc on the CSL and with regular s54 and baby and mild cams work ok with MAF on it.
Inline__engine said:
stevesingo said:
The point I am getting at is why?
If MAP is being used as the load reference for the ECU, then you can run into problems which worsen low speed operation. The ECU sample rate of the MAP sensor is fixed. The MAP is not for a given engine speed. You get pulses of MAP depression as each cylinder goes through the intake stroke, thereofor the MAP the ECU sees is not representative of true cylinder filling.
I have logged MAP on my engine and at low engine speed I can clearly see the MAP oscillating in time with rpm. Only when the rpm rises above the ECU sample rate does the MAP reading smooth out.
Likewise with MAF and long cams, the reversion pulses oscillate up and down the intake tract. The same air can pass the MAF sensor more than once. The ECU thinks there is more air entering the cylinders than actually is.
This is the same for plenum intakes and ITBs.
Changing to ITBs appears to help as it is normally done in conjunction with a swap the A/N (TPS/RPM), where TPS is the load reference. If you can't accurately measure the air entering the engine, then don't. Create a map based on the TPS as load.
No answer yet as to ECU type or load ref.
It may be using a torque demand map, where throttle opening (DBW), inj PW, Inj timing and ignition timing are calculated to deliver the torque demanded. In this instance, the quantity of air entering the engine must be measured, or referred to an VE model in the ECU and corrected against measured data, one channel being mass air flow.
it seems like you are more talking about the load sensor strategy If MAP is being used as the load reference for the ECU, then you can run into problems which worsen low speed operation. The ECU sample rate of the MAP sensor is fixed. The MAP is not for a given engine speed. You get pulses of MAP depression as each cylinder goes through the intake stroke, thereofor the MAP the ECU sees is not representative of true cylinder filling.
I have logged MAP on my engine and at low engine speed I can clearly see the MAP oscillating in time with rpm. Only when the rpm rises above the ECU sample rate does the MAP reading smooth out.
Likewise with MAF and long cams, the reversion pulses oscillate up and down the intake tract. The same air can pass the MAF sensor more than once. The ECU thinks there is more air entering the cylinders than actually is.
This is the same for plenum intakes and ITBs.
Changing to ITBs appears to help as it is normally done in conjunction with a swap the A/N (TPS/RPM), where TPS is the load reference. If you can't accurately measure the air entering the engine, then don't. Create a map based on the TPS as load.
No answer yet as to ECU type or load ref.
It may be using a torque demand map, where throttle opening (DBW), inj PW, Inj timing and ignition timing are calculated to deliver the torque demanded. In this instance, the quantity of air entering the engine must be measured, or referred to an VE model in the ECU and corrected against measured data, one channel being mass air flow.
at idle part throttle the blade helps stop the reversion by physically blocking waves (partially) and helps to isolate each runner from each other when a common air box is used. When you go WOT the blade doesn't stop reversion anymore and with a mild volume airbox there is still some communication across runners so its no different o most other common box setups. A true IR has infinite volume airbox so the runners dont cross talk unless you run a small manifold log for idle control or map signal
MAP for primary load sources on ITB is not the best unless the ECU can sample at a specified crank angle to capture the meaningful part of the signal. That's why most use Alpha N as an aftermarket ECU is often getting fitted which doesn't have the proper sampling capability for the job. You can sample from all runners to a common small plenum but the resolution of the signal is pretty poor IMO (can stop pulsing for the most part with appropriate small restrictor) such that Alpha N just works better anyway and better again with a MAP correction. Similarity reversion can make a MAF confused but when you talk race cams and ITB a MAF is not normally used. BMW used an Alpha-N with MAP correction system iirc on the CSL and with regular s54 and baby and mild cams work ok with MAF on it.
But we don't know what load source is being used in this application.
stevesingo said:
Exactly my point. ITBs on their own don't improve idle and the lack their of in this application may not be the reason for poor idle and low speed running. It may be that the ECU load source is not compatible with the longer duration cams with increased overlap.
But we don't know what load source is being used in this application.
they do improve idle and part throttle, they will always idle better than common throttle body setups when both are tuned correctly they are always better. you can of course screw things up but thats the user error.But we don't know what load source is being used in this application.
my current engine was single throttle that i ran on AFM, Alpha-N and MAP at various stages and now are ITB on MAP and Alpha-N at various stages and its significantly better no question at all
Indeed, if you don't believe us would you believe:
Max_Torque said:
to be honest these days, the only reason you'd run ITBs is to allow you to run a REALLY hairy cam! (Because the small downstream ((of the throttle plates) volume means at low speed you get a much smoother running engine as the internal EGR is prevented from getting back up into the plenum.
Modern throttles on modern plenums (big volume!) make good power these days, ITBs really are not needed ime.
if you want to do it properly, take a leaf out of BMWs book and use an M5 electronic throttle actuator to drive the throttles:
From here, but there isn't much else of use there: https://www.pistonheads.com/gassing/topic.asp?h=0&...Modern throttles on modern plenums (big volume!) make good power these days, ITBs really are not needed ime.
if you want to do it properly, take a leaf out of BMWs book and use an M5 electronic throttle actuator to drive the throttles:
stevesingo said:
276deg@ 0.1deg is not REALLY hairy though is it.
You still haven't answered what you are using for load on the ECU.
its not about duration. its more about the lift at TDC (overlap) for idle 3 mm at TDC on a 4V (which flow well at low lifts) is a fair amount with a common plenum single throttle. Easy to manage with ITB'sYou still haven't answered what you are using for load on the ECU.
Edited by Inline__engine on Thursday 16th January 21:45
Evoluzione said:
Starting to get some members. I'm there but shall listen to the experts, lol!stevesingo said:
276deg@ 0.1deg is not REALLY hairy though is it.
You still haven't answered what you are using for load on the ECU.
With 12mm of lift it is and the exhaust cam is a heck of a lot more too.You still haven't answered what you are using for load on the ECU.
It uses Maf for load so I think you're barking up the wrong tree there i'm afraid.
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