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Power curves 4 valver vs 2 valver by cvxjet
Started on: 10-30-2019 01:24 PM
Replies: 11 (248 views)
Last post by: La fiera on 11-04-2019 06:59 PM
cvxjet
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Report this Post10-30-2019 01:24 PM Click Here to See the Profile for cvxjetClick Here to Email cvxjetSend a Private Message to cvxjetEdit/Delete MessageReply w/QuoteDirect Link to This Post

I will probably catch some heck for this post, but I was doing some research and found out some interesting info. A few years ago ano acquaintance told me of how superior his Honda Del Sol engine was...A 1.6 liter engine that developed 160 hp....I doubted that this was all that good...So I looked at how the power was delivered over the rpm....Here is the info I came up with;

I compared the power curve of my 3.4L F-body conversion-Fiero engine with a Honda Del Sol 1.6 L engine- They both make approximately 160 HP....My Fiero 3.4 at 4500 and the Honda 1.6 L at 7500 RPM........Looking at the power band, I found that my 3.4 makes over 100 HP from 2600 to 5000 RPM, while the Honda doesn't clear 100 HP until 6000 RPM....So, right off you can see that my Engine is over 100 HP for a 2400 RPM spread while the Honda only clears 100 HP for 1500 RPM.....Worse though, is that while my engine is over 100 HP for almost half of the total rev band, the Honda is above 100 HP for only one FIFTH of it's rev band...Basically, it acts more like a light switch.

I calculated the over-100 hp-RPM band through the two transmissions (Getrag 5 spd vs Honda Del Sol 5 spd), but converted it to road speed.....


Car; Fiero

First Gear 15 to 30 MPH

Overlap; 5 MPH

Second Gear 25 to 50 MPH

Overlap; 12 MPH

Third Gear 38 to 75 MPH

Overlap; 20 MPH

Forth Gear 55 to 110 MPH

Overlap; 38 MPH

Fifth Gear 72 to 144 MPH


Car; Del Sol

First Gear 28 to 36 MPH

Overlap; -13 MPH

Second Gear 49 to 63 MPH

Overlap; -12 MPH

Third Gear 75 to 94 MPH

Overlap; -5 MPH

Forth Gear 101 to 127 MPH

Overlap; -4 MPH

Fifth Gear 131 to 164 MPH


As you can see, the Fiero 3.4 Getrag 5 spd stays easily above 100 hp when shifting through the gears- actually with substantial overlap, while the Honda Del Sol drops below on every shift- probably down to around 80 hp at each shift.....This clearly demonstrates that a wide power band is just as important- if not more so, than peak power....

Another comparison- The new Camaro SS, with the pushrod LT V8 is BOTH quicker and gets better MPG than the new Coyote 4V V8- powered Mustang GT. (The cars both have 6 spd manuals, and weigh approx' 3800 lbs)

[This message has been edited by cvxjet (edited 10-30-2019).]

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Flying_Dan
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Report this Post10-30-2019 02:21 PM Click Here to See the Profile for Flying_DanClick Here to Email Flying_DanSend a Private Message to Flying_DanEdit/Delete MessageReply w/QuoteDirect Link to This Post

Generally -

Torque = Acceleration
HP = Top Speed

I had a Caddy Formula 5spd for 8 years. I liked the lazy low-end and V8 rumble, but admit having to shift at 3500RPM was a bit annoying.

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Blacktree
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Report this Post10-31-2019 09:03 AM Click Here to See the Profile for BlacktreeClick Here to visit Blacktree's HomePageClick Here to Email BlacktreeSend a Private Message to BlacktreeEdit/Delete MessageReply w/QuoteDirect Link to This Post

A small high-RPM engine is generally not good for mid-range torque. And mid-range torque is what you mostly use during daily driving. This is pretty well known.

That said, those little 4-valve engines respond really well to forced induction. Even a modest size turbo can improve the mid-range torque considerably.

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cvxjet
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Report this Post11-01-2019 11:52 PM Click Here to See the Profile for cvxjetClick Here to Email cvxjetSend a Private Message to cvxjetEdit/Delete MessageReply w/QuoteDirect Link to This Post

The problem with a turbo is turbo lag- "There is no replacement for displacement"...Actually, in a truck or family car, a turbo is great because you are not worried about good throttle response- But in a sports car dicing thru turns, you need accurate throttle response.

That being said, they are now coming out with turbos with electric motors for initial response. When I was in HS (Back (Oh Crap!) 40 years ago) I thought up a "Turbo-supercharger" A turbo, but with a belt drive and clutch- when you first nail the throttle, the clutch would engage and drive the turbo, then as the exhaust came into play, the turbo would freewheel beyond the belt drive RPM...I even sent letters to Ak Miller and other Turbo co.s...they all basically stated "What Turbo lag?"

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wftb
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Report this Post11-02-2019 11:51 AM Click Here to See the Profile for wftbClick Here to Email wftbSend a Private Message to wftbEdit/Delete MessageReply w/QuoteDirect Link to This Post

Turbo lag is barely noticeable, even without the gimmicks. With drive by wire and newer small turbos combined with electronic boost control and DI, new turbocharged gasoline engines develop full torque at very low rpm's, a lot lower than an NA motor. On a track it means a broad torque curve with less shifting.

------------------
86 GT built 2.2 ecotec turbo
rear SLA suspension
QA1 coilovers on tube arms

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Dennis LaGrua
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Report this Post11-02-2019 12:34 PM Click Here to See the Profile for Dennis LaGruaClick Here to Email Dennis LaGruaSend a Private Message to Dennis LaGruaEdit/Delete MessageReply w/QuoteDirect Link to This Post

If you wish to make a comparison on 2 valve vs 4 valve the best examples are the 3.4TDC and 3.4L P/R engines. Both have the same displacement, use the same block but IIRC different cam timing.
3.4L P/R engine specs
160 HP @4600 RPM
200 ft lbs @ 3600 RPM

3.4TDC (DOHC) engine specs
Final Version LQ1 1986-1987
215 HP @ 5200 RPM
220 ft lbs @4000 RPM

Don't have the power curves but it looks like the torque and horsepower of the LQ1 higher in the RPM band. .

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

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pmbrunelle
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Report this Post11-02-2019 06:52 PM Click Here to See the Profile for pmbrunelleClick Here to Email pmbrunelleSend a Private Message to pmbrunelleEdit/Delete MessageReply w/QuoteDirect Link to This Post

 
quote
Originally posted by wftb:

Turbo lag is barely noticeable, even without the gimmicks. With drive by wire and newer small turbos combined with electronic boost control and DI, new turbocharged gasoline engines develop full torque at very low rpm's, a lot lower than an NA motor. On a track it means a broad torque curve with less shifting.



I drove a 2015 VW 1.8 TSI Golf, and it had like two seconds of turbo lag at low RPM.

Going up a hill in high gear at 1500 RPM or so, I noticed that after a step change in throttle position, it look some 2 seconds for the torque output to stabilize.

Definately noticeable. NA doesn't do that. Torque immediately stabilizes following throttle input.

Maybe there are some other modern cars that are less laggy; I don't know.

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La fiera
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Report this Post11-02-2019 07:33 PM Click Here to See the Profile for La fieraSend a Private Message to La fieraEdit/Delete MessageReply w/QuoteDirect Link to This Post

My Abarth with the tiny stock turbo has very noticeble turbo lag. I had customers with very powerful cars. One had a
911 AWD twin turbo with 800WHP and it was a rocket! Another had a Dodge Spirit R/T with 400WHP. I built a short block for a
700WHP Nissan K24. And all were powerful but had one comon denominator, LAG. They needed more time to deliver their full power.
With this knowledge I was armed to built an NA engine for my Fiero to take advantage where the all these turbo engines lack.
I proved this theory when I built an LT1 377 Stroker 6 speed manual for my neigbour. That thing would outrun anything, off the line
and had some legs to stretch also! With only 450WHP and 500WTQ, everything it raced against he won, if it had the right
suspension it would pop wheelies!
Why? Because of the rate of speed at what the power and torque was delivered. So, my approach is whatever power you make, delivery it fast!

[This message has been edited by La fiera (edited 11-02-2019).]

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cvxjet
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Report this Post11-02-2019 08:55 PM Click Here to See the Profile for cvxjetClick Here to Email cvxjetSend a Private Message to cvxjetEdit/Delete MessageReply w/QuoteDirect Link to This Post

There are situations where the turbo lag shows up...and others where it is barely noticeable.

As far as the 3.4 TDC vs 3.4..Consider the 3500......210 hp and 220 Lb/Ft of torque....With 90% of it's torque from 1500 to 5500....Tops out at 6300 rpm. And the 3400 actually put out 185 HP and 210 Lb/Ft of torque (Topping out at 6000)

Here is an interesting fact; The old Ford 351 Cleveland 4 bbl heads actually breath BETTER (On the intake side) than the new Coyote 5.0 4-valver....(the exhaust sucks because of the 1st gen Mustang spring towers which force the ports to turn sharply down)

Another interesting fact; The 5.7 Toyota Tundra engine doesn't breath as well as the 6.2 GM V8 in the Silverado.

The sad truth is the 3800 V6 beat everything on the road but was a sales disaster because "Common Knowledge" is that "4 valvers are FAR superior to them old 2 valve pushrodders!!"

To clarify, I would always use 4 valve tech on four cylinder engines in small cars, but I would (Also always) use a 2 valve PUSHROD engine in a truck...Those are the two extremes- the middle ground would be on a case-by-case basis (But you have to sell to the public- so whatever they believe is the end of the matter)

[This message has been edited by cvxjet (edited 11-02-2019).]

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Francis T
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Report this Post11-04-2019 08:41 AM Click Here to See the Profile for Francis TClick Here to visit Francis T's HomePageClick Here to Email Francis TSend a Private Message to Francis TEdit/Delete MessageReply w/QuoteDirect Link to This Post

It's about usable power; which GM's 2.8, 3.4s etc don't have much of above 4.5K !
Due in no small part to their god-awful intake and exhaust manifold designs!
Whereas, GM wanted an engine that would fit in any car, thus the very restrictive
manifolds!

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Gall757
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Report this Post11-04-2019 10:47 AM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post

I remember my 1985 Chrysler LeBaron sedan (2 valves per cylinder)......the turbo lag could have killed me on more than one occasion. I now have an Audi 2.0T. (4 valves per cylinder)....I forget it has a turbo for months. It is fast and reliable over a wide range. Turbos (when used correctly) still have a bad reputation to overcome.

[This message has been edited by Gall757 (edited 11-04-2019).]

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La fiera
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Report this Post11-04-2019 06:59 PM Click Here to See the Profile for La fieraSend a Private Message to La fieraEdit/Delete MessageReply w/QuoteDirect Link to This Post

 
quote
Originally posted by Gall757:

I remember my 1985 Chrysler LeBaron sedan (2 valves per cylinder)......the turbo lag could have killed me on more than one occasion. I now have an Audi 2.0T. (4 valves per cylinder)....I forget it has a turbo for months. It is fast and reliable over a wide range. Turbos (when used correctly) still have a bad reputation to overcome.



I had one of those! Well, not the LeBaron but a 1989 Dodge Spirit SE 2.5 SOHC, bacically the same motor. With a T61 turbo I ended up with 437WHP and 510WTQ @ 4500rpm.
Too much power, brutal. I didn't have the transmission and LSD to put this power down. After this I said screw that I can be faster with a 300WHP NA motor in the Fiero!

[This message has been edited by La fiera (edited 11-04-2019).]

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