Chad,
I am enjoying the conservation, the whole thread has been educational for me
Moderator: Team
Chad,
It was at about 600 rpm per second acceleration sweep rate on a Stuska dyno (with an inertia factor ).Stan Weiss wrote: ↑Tue Nov 26, 2019 12:19 pm Just what kind of dyno testing do you do? Are you using a inertia type dyno which lets the engine have a variable acceleration rate like it will on a drag strip or the standard 300 or 600 rpm per second tests?
Stan
2 x thoughts-testing at higher depressions??steve cowan wrote: ↑Tue Nov 26, 2019 12:08 pm Randy,
i just re-read the 2017 EMC thread again,great thread
interesting chat about oil pump and pressure,vac pumps and oil pans,really enjoyed the read and also read the magazine article on your 2011 383 that made 606hp.
on the 2017 emc thread one of your closing statements was-
ONE OVERLOOKED FACTOR IN MAKING POWER AT EMC TYPE RPM IS LACK OF DEPRESSION NOT LACK OF CFM.
can you expand on this -
It's really time based. Down at 3000 or 4000 rpm it isn't hard to supply air to an engine, it's harder to create depression.steve cowan wrote: ↑Tue Nov 26, 2019 12:08 pm Randy,
i just re-read the 2017 EMC thread again,great thread
interesting chat about oil pump and pressure,vac pumps and oil pans,really enjoyed the read and also read the magazine article on your 2011 383 that made 606hp.
on the 2017 emc thread one of your closing statements was-
ONE OVERLOOKED FACTOR IN MAKING POWER AT EMC TYPE RPM IS LACK OF DEPRESSION NOT LACK OF CFM.
can you expand on this -
700 @ what rpm?SpeierRacingHeads wrote: ↑Mon Nov 25, 2019 10:41 amChris Cobb has a 383 in the works right now and the goal is 700.. I will be sure to post it up so the house mafia can pick it apart.PRH wrote: ↑Mon Nov 25, 2019 10:34 am Maybe I’m not being analytical enough, and just going by what I “think” the results would be.
But here’s how I see it......
Chads heads have already shown they can make 675hp on a 383.
Not trying to take anything away from Steve’s efforts here, but if he ends up with what he says he’s shooting for......which is starting out with a Dart SHP 180 head, doing some rework to arrive at 270-280cfm with a finished runner volume in the 200-ish cc range....... and you removed the SRH 205’s from that 675hp 383 and swapped them for Steve’s Dart’s....... I’d be expecting the motor to take a pretty big hit in the HP dept.
I can agree with this. Or even possibly a head that is slightly undersized for your "6500" rpm target meeting it by means of very good discharge coefficient. But what part of the port do you focus this dc at? Throat, window, window at what lift, pinch if not at throat? Getting it real high in one of these areas will most likely compromise it elsewhere in the port.
Seems like you're not grasping what he's saying by this comment. How can he be part of something that actively bashes him whenever possible? The disdain they have for him is quite clear cut. <shrug>
bigjoe1 wrote:By the way, I had a long talk with Harold(Brookshire) last year at the PRI show. We met at the airport and he told me everything he knew about everything.It was a nice visit. JOE SHERMAN RACING
This is the direction I was thinking my post/questions would head.digger wrote: ↑Thu Nov 28, 2019 4:43 pm IMO it comes down to efficiency (discharge coefficient) at low rpm as the port might be be designed to move air for maximum power at 6500 rpm but at 3000 rpm its effectively way too large.
at 'low' rpm a larger size, higher flowing head will mean less depression (less resistance to flow) on the running engine but its got more area. so does the the smaller depression acting on larger area create more mass flow?
or does a smaller size lower flowing head that results in a higher depression (more Resistance to flow) acting on a smaller area result in more mass flow?
so if the larger port is 10% larger how much less depression will it see for the same operating point, rate of change of swept volume etc? 5% 10% 20%?
Not sure if this is what you are talking about. This is still a work in progress. The cfm is the peak piston flow demand at the listed RPM and the speeds / DC for the different places.digger wrote: ↑Thu Nov 28, 2019 4:43 pm IMO it comes down to efficiency (discharge coefficient) at low rpm as the port might be be designed to move air for maximum power at 6500 rpm but at 3000 rpm its effectively way too large.
at 'low' rpm a larger size, higher flowing head will mean less depression (less resistance to flow) on the running engine but its got more area. so does the the smaller depression acting on larger area create more mass flow?
or does a smaller size lower flowing head that results in a higher depression (more Resistance to flow) acting on a smaller area result in more mass flow?
so if the larger port is 10% larger how much less depression will it see for the same operating point, rate of change of swept volume etc? 5% 10% 20%?
Code: Select all
_____Intake_______---_Throat_--____----_Valve_---____----_MCSA_----__----_CFM_per_Sq._In._----_
__RPM____CFM______fps_______DC______fps_______DC______fps_______DC____Throat____Valve____MCSA_
2000.0___77.1___72.229___0.2062___57.748___0.1649___74.366___0.2123___30.095___24.062___30.986
2500.0___96.4___90.286___0.2577___72.185___0.2061___92.957___0.2654___37.619___30.077___38.732
3000.0__115.7__108.343___0.3093___86.622___0.2473__111.548___0.3184___45.143___36.093___46.478
3500.0__134.9__126.400___0.3608__101.059___0.2885__130.140___0.3715___52.667___42.108___54.225
4000.0__154.2__144.457___0.4124__115.496___0.3297__148.731___0.4246___60.190___48.123___61.971
4500.0__173.5__162.514___0.4639__129.933___0.3709__167.323___0.4777___67.714___54.139___69.718
5000.0__192.8__180.571___0.5155__144.370___0.4121__185.914___0.5307___75.238___60.154___77.464
5500.0__212.1__198.628___0.5670__158.807___0.4533__204.505___0.5838___82.762___66.170___85.211
6000.0__231.3__216.686___0.6186__173.244___0.4946__223.097___0.6369___90.286___72.185___92.957
6500.0__250.6__234.743___0.6701__187.681___0.5358__241.688___0.6900___97.809___78.201__100.703
7000.0__269.9__252.800___0.7217__202.118___0.5770__260.280___0.7430__105.333___84.216__108.450
7500.0__289.2__270.857___0.7732__216.555___0.6182__278.871___0.7961__112.857___90.231__116.196
8000.0__308.4__288.914___0.8248__230.992___0.6594__297.462___0.8492__120.381___96.247__123.943
8500.0__327.7__306.971___0.8763__245.429___0.7006__316.054___0.9022__127.905__102.262__131.689
9000.0__347.0__325.028___0.9279__259.866___0.7418__334.645___0.9553__135.429__108.278__139.435
9500.0__366.3__343.086___0.9794__274.303___0.7831__353.236___1.0084__142.952__114.293__147.182
Avg_____221.7__207.657___0.5928__166.026___0.4740__213.801___0.6103___86.524___69.177___89.084
I think the difficulty of answering these questions is that for any example given someone else can give an example that is counter to what one thinks is best, at least in actual on track performance, the dyno may say something different, not sure how much one truly reflects the other.digger wrote: ↑Thu Nov 28, 2019 4:43 pm IMO it comes down to efficiency (discharge coefficient) at low rpm as the port might be be designed to move air for maximum power at 6500 rpm but at 3000 rpm its effectively way too large.
at 'low' rpm a larger size, higher flowing head will mean less depression (less resistance to flow) on the running engine but its got more area. so does the the smaller depression acting on larger area create more mass flow?
or does a smaller size lower flowing head that results in a higher depression (more Resistance to flow) acting on a smaller area result in more mass flow?
so if the larger port is 10% larger how much less depression will it see for the same operating point, rate of change of swept volume etc? 5% 10% 20%?