well you answered your own question jz head flows much better= faster spool. also little things like no afm less restriction. better ignition system (separate coils for each cylinder)

 

the jz is a much better flowing engine, there a several major components affecting it, exhaust manifold, intake manidfold, head and well it's easier to make a 320 hp car respond better to a turbo than on a car that came with 230 hp. And of course the newer technology.

 

Oh boy, another 7M vs. 2J thread.

Who said you can't put the same turbos MK4s use on MK3s?

Drop some coin on headwork.

 

Most of the difference is in the head and cams.

 

Most of the difference is in the head and cams.

Does the shorter stroke have any affect?

 

Here we go again...It's all in the headwork and cam set-up. Spend the money to put a big turbo on a 7M and it will perform the same as a 2J...ported and polished head with oversized valves = same flow as a 2J head. Oh and don't forget about the superior technology ...

Khris

 

2 things.... head flow, and rod ratio .... both things that are better on a 2J

 

2 things.... head flow, and rod ratio .... both things that are better on a 2J

i knew that! so i did somethign about it!

 

i knew that! so i did somethign about it!

lol..you dog!!

 

i think zz_denis put a turbo on his car that MKIV's usally run and he was saying how his spooled faster on his 7m then it did on 2jz's. but i can't rem. what type of turbo it was though.

also like osfast7m said in the other thread the 2jz is meant to run more 11 lbs. of boost stock; therefore, it has a better flowing STOCK head. but if you do as he said and put money into it then the 7m will do just as well.

nigel

 

Damn that was fast...

Thank you to all that replied.

When I said the thing about the cars not able to use the same turbos I ment why do you always see the jzs runnin' bigger turbos...

And again thank you all, lol, Im startin' to like this site...

 

When I said the thing about the cars not able to use the same turbos I ment why do you always see the jzs runnin' bigger turbos...

its another one of those money things. only a few 7m owners put that much money into there car to run bigger turbos. some also run big turbos like the MKIV's do but they may have a diff. name and thats not as big therefore people won't think there as good.

nigel

 

There's too many varibles in the stock setups to accurately compare the two.

Exhaust and intercooler piping have a big effect on spool. 2Jz's intercooler piping is much shorter than the 7m. Most 2jz exhaust systems are much larger diameter than the 7m.

Other things that effect spool are:

2jzs small turbos in squence spool faster than a Ct26.

Cams and bigger valves actually slow spool somewhat.

The stock 2jz engine management advances timing thus aiding spool.

The 7m's longer stroke = higher piston speed should should better spool than the 2jz (all things being equal)

The only true way to measure spool between the two would be to hook both engines up to affermarket engine management, the same turbo, ignition, and intercoolers....

 

Based on dyno graphs that I have seen in the tuning sectiion, I'm not sure the 2Jz does spool turbos better than the 7M. The one comparison that comes to mind is the spoolup of the SP57 turbo. I have never seen a 2JZ engine have as good of a dyno chart as DR Jones with his SP57.

The way I see it, is that the higher flowing head of the 2JZ will only slow air velocities down at low revs. While the 7M will squeeze the air out at a higher rate spinning the turbine faster at low revs. Just my theory.

 

7m = longer stroke = will spool turbo faster then 2jz in the long run.

required headwork/valve work of course will be needed for bigger turbos and bigger flowing needs.

for smaller turbos the 7m is gonna spool faster. I think thats one of the 7m's bigger advatanges over the 2jz...its longer stroke

 

7m = longer stroke = will spool turbo faster then 2jz in the long run.

nope, 2JZ = smaller rod ratio = moves air more quickly at lower RPMs + better head flow = spools any turbo faster

stroke means nothing unless compared to rod length when speaking in terms of air flow

 

i dare you to find a 2J running the SP57 that spools faster than mine....leave the bench racing @ home.

 

The 7m's longer stroke = higher piston speed should should better spool than the 2jz (all things being equal)

nope, 2JZ = smaller rod ratio = moves air more quickly at lower RPMs + better head flow = spools any turbo faster

stroke means nothing unless compared to rod length when speaking in terms of air flow

Well Im getting two answers here...

To me it would seem that the longer stroke would help spool because the pistons would have to move a longer distance every time the crankshaft spun once as compared to the jz with the smaller crank thus moving more air....

Is there any place I can see dyno graphs of a 7m and a 2jz spooling up the same turbo?

Thank you all for your replies...

 

I've gotten comments from a few MKIV owners that my T76 spools pretty quick being on a 7M, this comparing it with a 2j of course. And I'm not even using the anti-lag. Head is STOCK but not the exhaust and intake manifolds. There has to be other variables, timing map, fuel mixtures, etc. If the 1j and 2j do really spool the same turbo faster than a 7m, stock for stock, I don't think it's the head flow alone that's doing it.

--Ron

 

Well Im getting two answers here...

To me it would seem that the longer stroke would help spool because the pistons would have to move a longer distance every time the crankshaft spun once as compared to the jz with the smaller crank thus moving more air....

Is there any place I can see dyno graphs of a 7m and a 2jz spooling up the same turbo?

Thank you all for your replies...

When thinking air flow, you must take into account the rod length. The length of the rod in relationship to the distance of the stroke determines how much time the piston spends accelerating and at what angle and speed. Engines of lower rod ratios will pump more air more quickly because the piston moves sooner. Engines with longer rods have more piston dwell time. This is the time in which the piston moves relatively slowly compared to crank rotation. These engines have slower piston acceleration and take longer to pump air than those comparatively shorter. Remember, when comparing the 7M and 2Jz, the displacement is the same, so despite the shorter stroke, the 2JZs larger bore create the same swept volume in the cylinder. The difference is that the 2JZ can move more air through that cylinder more quickly at lower RPMs than the 7M can due to it’s geometry. Add to this the fact that the head design of the 2JZ is significantly better than the 7M and it’s simple to see why it flows more air and therefore, will spool a turbo faster. The head’s superior design has little to do with valve size also. The shape of the ports is the most significant advantage. The JZ heads having a distinct “D” shape to their inlet ports, a trait that all performance heads of modern design have and a design that’s proven to flow much more than any other shape. This is not to discredit the advantage of larger valves, bust simply to point out that fitting larger valves to a 7M head will not yield equivalent flow to a JZ head. Add to this equation differences in valve event timing to coincide with the advantages of geometry and flow in the JZ engine and you simply have a superior design that flows more air.

BTW, back on rod ratio. The 2JZ has a rod ratio of 1.65 which is considered “ideal” by the automotive engineering community. It’s the ratio that proves most efficient for operating ranges in street driven cars on gasoline. The 7M on the other had has a rod ratio of 1.675, not significantly higher numerically, but a significant change in geometry.

Note that with this whole rod ratio thing we’re not talking about the force applied on the crank here. That’s an entirely different story. The longer stroke create a longer lever which allows the 7M to apply more force to turn the crank during the power stroke and therefore allowing the 7M to do more work for the same applied piston force (that’s key, remember that for later). This is a great asset to have in an engine and helps produce lots of torque, but has nothing to do with pumping air through the engine, and therefore spinning a turbine.


Also remember that there are many other things that contribute to how quickly a turbine will accelerate. Many of these things can not really be compared engine to engine. What causes a turbine to spin is the pressure drop across the turbine. The greater this is, the faster it will accelerate. The shape and size of the exhaust will have a lot to do with this as we all know. Generally a turbo placed more closely to the exhaust valves will accelerate faster. The use of exhaust pulses also has an effect (this is what split turbines are all about). Exhaust pulses are dictated by valve timing though, so cam timing now effects the equation. Manifold design the size/existence of reversion damns and collector design will all have an effect. The more heat energy that can travel with the exhaust gasses will cause the gasses to flow faster (header wrap, turbo bags and ceramic coatings). These are all factors that are likely to be different between two setups on different engines. All of these things make it rear impossible to compare apples to apples. The turbo being exactly the same, there are simply to many other variables to make a good comparison.


Did that help?

 

Did that help?

lol, Yes thank you very much...

edit: djonez your graph is the shit...

 

thanks man, i try.

 

Hey Dr. J, at what psi did you produce that beatiful graph at? Oh, BTW, you still haven't gotten back to me about those rods you had....

 

20 psi, sub 10 A/F. that's OLD dyno stuff...see my site for a full writeup, etc.

sorry about not getting back to you, i purged my PM box a while back and may have deleted the PM. i just checked and i don't have any more rods. sorry man.

 

head design... the 2J head flows a significantly larger CFM rating that the 7M does...

massage the 7M head, port the lower manifold and use a FFI upper... use a tubular exhaust manifold... youll spool an equivalent turbo just as fast as a 2J if not faster.

the question as to whether a longer exhaust pulse is better than a shorter pulse is a good one.