dr_frankenstein
Mad Scientist
- Joined
- Mar 17, 2008
Go on...... Cstravo you have our ears.
Can someone explain why stage II heads are not streetable?
- Thread starter norbs
- Start date
On one of mine it took 28-29psi to make 700whp. With a smaller displacement engine is expect more hp though at higher pressure ratios.At what rpm/boost was that achieved ???
What mods were done to the engine/heads ???
Just asking because maybe I'll swith over to a toyota 3.4 in the future.
robzombie
Well-Known Member
- Joined
- Oct 10, 2012
I know, I was being sarcastic.
I should use modicons more often or something to get across what I'm really conveying.I was hoping that he would post that rpms were 2/3 g higher and the such to show that it's an apples oranges comparison.
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FYI, a supra made 1185 RWHP on e 85 with the present turbo I am using, so the turbo is a very capable piece. As for my combo with the cam that is in the car, I just don;t know the results until I dyno it. I ran out of time last year, due to a string of complications. Not sure how critical the cam is for low speed torque when the heads are monsterous. TO clear things up, its a 3.8 with a 2.02, 1.6 valve, 235 seat, 600 open with 7/16..165 thick pushrods with a 1.71 rocker ratio...with a quick spool valve with a split turbine. 1.44 AR. 81MM exhaust turbine wheel. Computer simluations show peak power at 7600 -8200 rpm.
Norb
Norb
Bison: If he's on turbobuick, ask him to start a thread...
150# seat force is the highest l've seen for the 3800.
Any good engineer should be able to quantify his statement...never mind qualify. Soft HOW? Are you just looking at advertised vs 0.050" vs 0.200" duration? Are you talking about acceleration, or jerk?
robzombie: Norbs' 3.8 has 16% more valve area than the 2JZ (2.02" vs 33.6mm). Yes, the 2JZ would make your car faster.
32 psig boost. 900 bhp
Norb: How was the low end torque on that Supra? Even with fast burn chambers and efficient ports, l bet it still didn't make more than 250 lb-ft.
Imagine filling a glass with water. Leave the tap open too long and it will just spill over. That's what your cam/valve is doing, because it's not cycling air fast enough until 5500 rpm (the 270 should hit at 4700 rpm with the same valve/cam). If you want to move the operating range lower, close the tap earlier - all else being equal. You'll be able to judge better after you dyno it.
Any good engineer should be able to quantify his statement...never mind qualify. Soft HOW? Are you just looking at advertised vs 0.050" vs 0.200" duration? Are you talking about acceleration, or jerk?
robzombie: Norbs' 3.8 has 16% more valve area than the 2JZ (2.02" vs 33.6mm). Yes, the 2JZ would make your car faster.
32 psig boost. 900 bhp
Norb: How was the low end torque on that Supra? Even with fast burn chambers and efficient ports, l bet it still didn't make more than 250 lb-ft.
Imagine filling a glass with water. Leave the tap open too long and it will just spill over. That's what your cam/valve is doing, because it's not cycling air fast enough until 5500 rpm (the 270 should hit at 4700 rpm with the same valve/cam). If you want to move the operating range lower, close the tap earlier - all else being equal. You'll be able to judge better after you dyno it.
turbobitt
Well-Known Member
- Joined
- Feb 14, 2002
Any good engineer would also not confuse his or her opinion with facts. That is exactly what your doing is expression your opinion as fact. You need to be very careful when giving out advise based on your opinions as to not steer them in the wrong direction just because you think it should be that way. You are being way to general with reference to aggressiveness on the mentioned cam lobes. Technology is moving forward and as a result our components become that much better. Companies like Comp Cams realizes this and provides a very wide range of lobe families for us to pick from. Our opinion on what was once aggressive is simply not the case anymore.
And when Bison and I talk about analyzing cams, let me assure you that we have a pretty good extensive library of lobes. All of them being what we consider turbo cams, and probably all you would consider to aggressive. Because of our own time and money we invested to do this research, our information is proprietary.
Allan G.
johnplogii
Senior citizen
- Joined
- Aug 13, 2005
Mine are 150#-160# on the seat. Never tried going past 7000 rpm, but it pulls strong right up to that.
turbobitt
Well-Known Member
- Joined
- Feb 14, 2002
I must be a bad engineer and wasted money on these 300+lb on the seat springs.
Speaking from personal experience, I been from 180# to 270# and can't quantify any gains but I also been pushing it harder as I been stepping up the hardware so its hard to say what is correct without any information on the combination.
I will say this, I was afraid of running the higher loads because of the type of driving I do but now that I have some real world data and experience I'm glad I have the extra insurance.
Allan G.
Sarcasm doesn't come across right, I don't follow the low spring pressure on a turbo car theory. I've got all the right valve train to go with the monster springs. As long as your valvetrain can handle it, I see no reason to not go too high on spring pressure.
I've had issues with valve spring pressure being too low before on a turbo car and it's quite obvious when it's too low (power drops off like a rock). I don't know all the details on my cam and springs, but I trust Chris Hogeland put the right stuff in it. I do know the cam is aggressive. Also remember, I'm running a 277" motor and a .85 A/R 3 bolt turbine housing with a little 68mm turbine. Next time my headers come off I'm putting a bung in put log backpresure. I expect it's pretty high.
I've had issues with valve spring pressure being too low before on a turbo car and it's quite obvious when it's too low (power drops off like a rock). I don't know all the details on my cam and springs, but I trust Chris Hogeland put the right stuff in it. I do know the cam is aggressive. Also remember, I'm running a 277" motor and a .85 A/R 3 bolt turbine housing with a little 68mm turbine. Next time my headers come off I'm putting a bung in put log backpresure. I expect it's pretty high.
turbobitt
Well-Known Member
- Joined
- Feb 14, 2002
What you guys do with those 3 bolt housings is amazing. I'm sure back pressure is high and as a result the proper cam timing is that much more important.
Allan G.
SOrry the supra made 1136, not 1185 HP, and 823 ft torque on E85. The point being is the airflow capacity of the turbine housing is all I am interested in. I know I will need the RPM, and Dusty has picked a good converter to do the Job. Cstavro, I won;t need a supra to make my setup work, I think it will be just fine, with 35-38 PSI boost this will come alive, no matter if the cam is not the best.
Which valve do you believe causes the valve control issue? Is it valve toss or valve bounce? Or another issue?
Conceptually: (not synonymous with "vague")
Brute force can be used to close the valve, then beef up the valvetrain to cope - at the expense of mass, cost, and friction. Adding mass compounds the valve control issue. The elegant solution is to use light and stiff valvetrain.
Seat force is not the most important figure for valve control (unless you try to hammer the exhaust valve open against high cylinder pressure). As far as large diameter, multi coil springs, sure. Comparing them to conical and bee hive springs is apples to oranges. I'm NOT saying to use any old spring. And l'm not saying the 150# will necessarily work with your existing valvetrain setup to the same RPM as your 240# springs.
Valve control is all about low mass and high stiffness, and a smooth cam profile. resonance is the biggest issue. When the spring hits resonance, you lose valve control. Are we all on the same page?
Physics 101: Frequency = 2*pi*sqrt(Stiffness/Mass). the higher the stiffness and lower the mass (of the whole system), the higher the resonance frequency (i.e. RPM). Spring mass counts, and the stiffer the spring, the stiffer the rest of the valvetrain needs to be - not just for deflection, but because accelerating the valve sends excitations through the entire valvetrain. Certainly valve loft is much worse than a few extra # spring pressure.
A spring is its own mass-damper system (mechanical control system). The lower the mass, the better. A conical spring (e.g. Comp #7230) has less mass than a cylindrical spring, uses a lighter retainer, and every coil has a different mass and stiffness - so they have a much higher resonance frequency (i.e. you can control the valve to higher RPM). Resonance is when the individual coils go crazy and do their own thing - you can observe the wave moving up and down the spring - and it cannot control the valve.
Ricardo WAVE cannot analyse pushrod systems. Sprintrons can analyse intake valve motion, but can't predict exhaust valve control (due to high cylinder pressure). There IS software that comes close. The best and brightest in the industry still use the race track as the ultimate test. Concepts guide us towards making informed decisions to come to a solution.
turbobitt
Well-Known Member
- Joined
- Feb 14, 2002
I was interested in your suggestion about the cam lobes and thought I would at least look into it. Now I know why I never gave these a second look. There is an immediate problem with using the EHI/EHX profiles as you suggest. Anyone care to guess ? Here is a hint. This is quoted directly from the comp catalog.
The EHI (intake) and EHX (exhaust) Series are higher ratio versions of the DHI and DHX hybrid hydraulic/solid roller designs.
These are intended for race applications that may see some street use or for other special applications with their primary emphasis
on performance without compromise for noise concerns. 27 MAI intake and 30 MAI exhaust. 2.036" Journal MINIMUM.
