Notices
Car Nitro & Gas Engines Discuss all aspects of Nitro and Gas rc car engines here!

Pull Starts

Old 08-02-2008, 11:04 AM
  #1  
kersplat
Senior Member
Thread Starter
 
kersplat's Avatar
 
Join Date: Aug 2004
Location: Lancaster Park, AB, CANADA
Posts: 340
Likes: 0
Received 0 Likes on 0 Posts
Default Pull Starts

I see a few people stating pull starts cause a loss in power. Unless you have a dyno, I seriously doubt it that anyone can tell the difference (in performance)between the engines with one and the engines with a standard backplate.For those who have an engine with a pullstarter they say "robs power".....Check your carb settings.[>:] I have two same vehicles ,"single speed " on each. One with a "pull start" OS 12 and one with a "Bump start" OS 12. Both cars have the EXACT same accelleration in a drag race side by side all the way at WOT. Can there be any better proof other than a .08 difference in BHP, found on a dyno? I think not. Really, in a race, it is not always the fastest car that wins. It is mostly the car with the most experienced driver.
Old 08-02-2008, 11:10 AM
  #2  
twomanytoys
Senior Member
 
Join Date: Jan 2007
Location: , PA
Posts: 5,382
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Pull Starts

Well other than hp ratings its a proven fact that you lose rpm's. In most cases it can be about 5000rpm's. Thats a huge power loss right there. It may not be a noticable in low rpm's but top speed will suffer.
Old 08-02-2008, 11:20 AM
  #3  
kersplat
Senior Member
Thread Starter
 
kersplat's Avatar
 
Join Date: Aug 2004
Location: Lancaster Park, AB, CANADA
Posts: 340
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Pull Starts

SPECIFICATIONS
OSMG2102
Displacement: 0.18 cu in (3.0 cc)
Bore: 0.629 in (16.0 mm)
Stroke: 0.590 in (15.0 mm)
Practical rpm: 3,000-32,000
Output: 1.35 hp @ 28,000 rpm NOTE THE NUMBERS!!!!!

Weight: 10.4 oz (296 g)
Includes: 203 air cleaner
Requires: glow plug, manifold and muffler or tuned pipe.
11881 18CV-RX ABC Parts listing

SPECIFICATIONS
Stock Number: OSMG2101
Displacement: 0.18 cu in (3.0 cc)
Bore: 0.629 in (16.0 mm)
Stroke: 0.590 in (15.0 mm)
Practical rpm: 3,000-32,000
Output: 1.35 hp @ 28,000 rpm NOTE THE NUMBERS!!!!!

Weight: 8.4 oz (238 g)
Includes: 203 air cleaner
Requires: glow plug, manifold and muffler or tuned pipe.
11870 18CV-R ABC Parts listing

These are dyno numbers. If these were false then it would be false advertising and a legal matter. DONT give in to race track rumors and BS!
Old 08-03-2008, 02:16 AM
  #4  
Spetz
Senior Member
 
Join Date: Sep 2007
Location: , CYPRUS
Posts: 2,032
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Pull Starts

I think the pullstart itself wont affect power, but it'll still make a difference in acceleration

It's just extra weight the engine has to accelerate. It's like adding heavier rims to a car. It wont "lose" power but of course it'll be slower as the engine will need to work harder to get the heavier bits to speed


As far as 5000rpm less... I really doubt there would be such a huge difference
And anyway, for there to be such a big difference, that means there would be so little power in those last 5000rpm that when driving that revrange would not only be useless but it would never get there, pull start or not.


I'm not saying pullstarts don't affect performance, but it's no huge deal, and it's a convinience thing.
That being said, when I added a lightweight flywheel I noticed my car was more responsive, so I am sure a bit of weight makes some difference
Old 08-03-2008, 06:31 AM
  #5  
iamnot
Senior Member
 
Join Date: Sep 2007
Location: noyb
Posts: 1,048
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Pull Starts

imho, tuning is far more important than whether an engine is bump or pull start
next (or maybe even first), in a race situation, would be driving ability.
then somewhere farther down the list would be how the engine was started

there's a condition in psychology that says
if you are expecting something to change
then you will very likely perceive that it has done what you expected

you can only reliably claim a performance increase by removing the flywheel
if someone else drove it before and after w/o ever knowing what was changed
or even if something was changed

you changed it expecting crisper response
therefor you preceive that response is crisper
Old 08-03-2008, 08:09 AM
  #6  
Spetz
Senior Member
 
Join Date: Sep 2007
Location: , CYPRUS
Posts: 2,032
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Pull Starts

I also retuned it once the new flywheel went on...
But, with my real car, when I swap rims over I most definately feel a difference
Old 08-03-2008, 09:39 AM
  #7  
twomanytoys
Senior Member
 
Join Date: Jan 2007
Location: , PA
Posts: 5,382
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Pull Starts

The one way shaft either inside or outside the case will decrease rpm output. Anything that has rotating mass will affect rpm's and power output. Install a larger heavier and smaller lighter flywheel on an engine and you will see what difference it makes.

Figure this one out then.

LRP Spec 3 Pull start
Power Output: 3.81 PS
Useable RPM Range: 2,000-33,0000
Engine Size: .28 cu in (4.58cc)
Bore: .73" (18.5mm)
Stroke: .63" (17mm)
Number of Ports: 6+1 (6 intake, 1 exhaust)

LRP Spec 3 Non Pull Start
Power output: 3.95 NPS
usable rpm range: 2,000-38,500
Engine Size: .28 cu in (4.58cc)
Bore: .73" (18.5mm)
Stroke: .63" (17mm)
Number of Ports: 6+1 (6 intake, 1 exhaust)
Old 08-03-2008, 10:21 AM
  #8  
Spetz
Senior Member
 
Join Date: Sep 2007
Location: , CYPRUS
Posts: 2,032
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Pull Starts

Twomanytoys,
Sure on paper/dyno there might be a difference
But what I was saying is, can you imagine how little power the engine is making past 33,000rpm for it not to be able to spin that extra bit of weight? If you take that into consideration, those extra 5000rpm are useless and will never be reached once you add car weight, tyre drag, driveline drag, wind drag etc
Like I said, at most it might make a small difference in acceleration
Old 08-04-2008, 11:05 AM
  #9  
378
My Feedback: (4)
 
378's Avatar
 
Join Date: Jan 2004
Location: Lebanon, TN
Posts: 2,861
Likes: 0
Received 2 Likes on 2 Posts
Default RE: Pull Starts

My OS 18 CV-RX can't even top itself out with the truck's load on it. I'm not losing any power to the recoil.



The ONLY way the recoil is going to affect performance is by adding another four ounces to the total vehicle weight. That's it. More dirt clings to the damn car if you run offroad!


Also, the recoil actually fell off my old NT16. Fell completely off, as in one-way was clear of the output shaft. Zero power increase. I didn't know it till I shut down three tanks later and found the recoil sitting free on the center driveshaft.


And for those of you bringing dyno graphs, remember that these little engines and dynos don't get along. One guy measures one engine, the next guy measures the same engine setup on a diff dyno and gets completely differant numbers, and then the next guy is running 30% instead of 20%, and the guy after that has a differant pipe. Same engine, differant testers, all radically differant numbers. The amount a pullstart can possibly draw falls well into the deep margin for error that dynoing these engines has. Hundreths of a horsepower? I highly doubt that is accurate to begin with...This also swings both ways. There's no telling what affected either dyno graph. I'm sure they're pretty close, probably down to the tenth of an HP....but we're talking a few hundreths here.


Edit: And if the one-way bushing sucks down 5 grand, the bushing sucks ass. That's all there is to it. I've always wondered why the startshaft never got a bearing, but instead got that bushing...
Old 08-04-2008, 11:40 AM
  #10  
Spetz
Senior Member
 
Join Date: Sep 2007
Location: , CYPRUS
Posts: 2,032
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Pull Starts

378,
The theory is not that the one way takes away so much power, but that the starting shaft does due to the added spinning weight.
Basically under acceleration the engine not only has to move the car but also accelerate an additional mass (the starting shaft)

Anyway though I also think the difference is too small to care about
Old 08-04-2008, 12:31 PM
  #11  
iamnot
Senior Member
 
Join Date: Sep 2007
Location: noyb
Posts: 1,048
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Pull Starts


ORIGINAL: Spetz

the difference is too small to care about

there ya go, right there

probably the smartest thing said in this thread
Old 08-04-2008, 12:55 PM
  #12  
Spetz
Senior Member
 
Join Date: Sep 2007
Location: , CYPRUS
Posts: 2,032
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Pull Starts

Yay I'm a genius!!
Old 08-04-2008, 01:36 PM
  #13  
kersplat
Senior Member
Thread Starter
 
kersplat's Avatar
 
Join Date: Aug 2004
Location: Lancaster Park, AB, CANADA
Posts: 340
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Pull Starts

LRP Spec 3 Pull start
Power Output: 3.81 PS
Useable RPM Range: 2,000-33,0000
Engine Size: .28 cu in (4.58cc) More conservative timing
Bore: .73" (18.5mm)
Stroke: .63" (17mm)
Number of Ports: 6+1 (6 intake, 1 exhaust)

LRP Spec 3 Non Pull Start
Power output: 3.95 NPS
usable rpm range: 2,000-38,500
Engine Size: .28 cu in (4.58cc) Higher more advanced port timing
Bore: .73" (18.5mm)
Stroke: .63" (17mm)
Number of Ports: 6+1 (6 intake, 1 exhaust)

The differences in RPM and BHP is NOT due to the pull starter.
Old 08-05-2008, 05:46 AM
  #14  
hspower
Junior Member
 
Join Date: Jul 2008
Location: billingham, UNITED KINGDOM
Posts: 18
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Pull Starts

spetz
Old 08-05-2008, 06:15 AM
  #15  
Spetz
Senior Member
 
Join Date: Sep 2007
Location: , CYPRUS
Posts: 2,032
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Pull Starts

Yeah?
Old 08-05-2008, 06:46 AM
  #16  
mordraid
Senior Member
 
Join Date: Jun 2006
Location: dolbeau-Mistassini, QC, CANADA
Posts: 392
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Pull Starts


ORIGINAL: twomanytoys


Figure this one out then.

LRP Spec 3 Pull start
Power Output: 3.81 PS
Useable RPM Range: 2,000-33,0000
Engine Size: .28 cu in (4.58cc)
Bore: .73" (18.5mm)
Stroke: .63" (17mm)
Number of Ports: 6+1 (6 intake, 1 exhaust)

LRP Spec 3 Non Pull Start
Power output: 3.95 NPS
usable rpm range: 2,000-38,500
Engine Size: .28 cu in (4.58cc)
Bore: .73" (18.5mm)
Stroke: .63" (17mm)
Number of Ports: 6+1 (6 intake, 1 exhaust)
Those aren't exactly the same engine. The one with the pull start is designed with lower RPM for monster truck ( who usually got 2 speeds) and the other is designed to go in truggies. That's why you see a 5000 rpm difference.

The pull start is (i my opinion) a way for a potential air leak. It is easier to have an air leak in the back plate with a plastic cap than with the original back plate.
Old 08-05-2008, 07:59 AM
  #17  
chookman46
Member
 
Join Date: Jun 2008
Location: Queensland, AUSTRALIA
Posts: 95
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Pull Starts

If you have a starter box and you can use it to start your car you are far better of with a bump start engine. Whether it is noticable or not you will have to agree it takes extra power to spin the shaft and the drag on the one way bearing. That is a fact whether you can tell the difference or not is debatable.

The main reasons I dont like pull starts is that they can be unreliable, OWB slipping, broken cord, broken springs. And the biggest problem is that its another place for a leak to occur. Have seen engines get dusted from sucking fine dust back in the pull start before.
Old 08-05-2008, 09:04 AM
  #18  
Spetz
Senior Member
 
Join Date: Sep 2007
Location: , CYPRUS
Posts: 2,032
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Pull Starts

The problem with bump start is lugging it around, especially if your car stalls a bit down the road where in reality all you need to carry is a glow plug
And also the initial cost. I don't know how much they cost but I assume the setup + battery would be at least 60-80 USD as opposed to just pull start which is $10 more or so

Though, I agree that it is a potential air leak. In fact mine leaked air and oil so I bought new backplate + starting shaft
Old 08-05-2008, 09:14 AM
  #19  
hrdcoreglf
Senior Member
 
Join Date: May 2007
Location: Boca Raton, FL
Posts: 1,106
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Pull Starts

It is not really about the loss of power, it is about the added potential for air leaks which can cause potential tuning problems. The pullstart itself is mostly plastic, so it is not very heavy, but the OWB and start shaft and backplate do add weight to the rear of the engine. If you can win with either engine it doesn't really matter. It is more driver than machine.

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.