Johnny Posted January 6, 2008 Report Share Posted January 6, 2008 I know that V-M has said that the N9Txx engine isn't suitable for high rpm because of heavy parts, but is 6500rpm the absolute max or is it possible to raise the rpm-limit to maybe, say 7000rpm? Quote Link to comment Share on other sites More sharing options...
august Posted January 7, 2008 Report Share Posted January 7, 2008 i know some of the race cars were revving to 7k, but i'm not sure what all was different with the motors. i'd imagine you could do it if it was well balanced!?! i remember having the valve springs tested when i had an N9T head tweaked at a machine shop in los angeles, and they were saying the springs were way strong enough to handle 6500rpm, so maybe you could even use stock valve springs? good question... why do you want to spin it to 7k anyway? (just curious) Quote Link to comment Share on other sites More sharing options...
Johnny Posted January 7, 2008 Author Report Share Posted January 7, 2008 If the stock springs would do the job, that'd be awesome! Why spin it to 7000rpm? I'm thinking that if you want lots of ponies you'd like to have the power higher up to avoid huge torque that would ruin the drivetrain. And when you have a turbo that spools pretty high up, (maybe 5000rpm?) the powerband would be too narrow. Also I saw a post on the Peugeot-L that someone (I think it was Joe Grubbs) thought that with the danielson cam it felt that the engine still was pulling pretty good at the rev limiter. Where is peak power at with the danielson-cam? Quote Link to comment Share on other sites More sharing options...
Bean Posted January 7, 2008 Report Share Posted January 7, 2008 Hi Johnny, The arguement to run a higher rpm to move the power up to save the drivetrain is a bit flawed... Doesn't matter if the car is being launched off the start - if a big power, big boost motor hits a massive peak at 6500 RPM, and you're pulling 2nd gear that torque is still being made and transmitted - so it would still destroy a weak drivetrain just as effectively... Many a modded car has taken out trannies when hitting boost alone at speed... The only thing that you're avoiding is the shock loading from it coming off the start / down low... So it might last a little longer - just not by much. I've never heard of the 505 drivetrain failing in one of these cars, except for the splines in the drive shaft - but 9/10 times the joints were dry and had worn to much causing the failure... If you were going for big power - I'd at the very least may sure they were well lubed with a high shear grease. BTW - another downside is a car that "feels" slower due to the turbo lag and lack of response... Sure it's faster at the drag track - but stock cars will feel faster in everyday driving. Rabin Quote Link to comment Share on other sites More sharing options...
Johnny Posted January 7, 2008 Author Report Share Posted January 7, 2008 Hi Rabin, Perhaps I was a bit too quick to write that... What I ment was that if I move up the powerband I can make more power without blowing the drivetrain. I'm fully aware that it will feel slower in everyday driving, but that's not what I want my car for. Back to topic! Do the stock valvesprings cope with 7000rpm? What is the limiting factor to high revs? If it is weight of internal parts, how will this show itself? Quote Link to comment Share on other sites More sharing options...
Bean Posted January 7, 2008 Report Share Posted January 7, 2008 Well - the only limiters will be valve float at high RPM, and the rotating assembly... From what I understand the Pug components are quite heavy - but it should be fine... If I were to hazard a guess - as long as you're running a cam that's breathing at 7000 RPM the engine should easily handle it - it is after all less than 1000 rpm over the OEM redline... The XN6 motor revs to ~ 7000 RPM before the valves float and limits RPM... (One of my buddies kept our dirt car pinned in a spin and that's how we found out!) So if the XN6 can do it without an issue the N9TE should have no problem. If you're into the motor though - balancing the pistons and the con rods would be recommended. Rabin Quote Link to comment Share on other sites More sharing options...
V-M Posted January 7, 2008 Report Share Posted January 7, 2008 Hint: Measure/calculate piston speed in that rev and google a bit about that. XN6 have bit lighter internal parts than N9T. I think head part is not limitting if that is good condition... Liners are not worn and cam gear is in good shape etc... Bottom will do 6500 easily if parts are balanced, well it will do without also but it will not last long. 7000 is bit tought one with original parts (one piston+con.rod weights 1.5kg when fex saab piston and conrod weights only 1.2kg) IMHO V-M Quote Link to comment Share on other sites More sharing options...
Johnny Posted January 8, 2008 Author Report Share Posted January 8, 2008 Would balancing the rods and pistons be enough or is it necessary to send the crank to balancing too? Thanks for the hint V-M, I appreciate your opinion. I calculated the piston-speed to 19m/s (3748ft/min) @ 7000rpm and from what I've read that should be ok? Quote Link to comment Share on other sites More sharing options...
V-M Posted January 9, 2008 Report Share Posted January 9, 2008 Would balancing the rods and pistons be enough or is it necessary to send the crank to balancing too? Thanks for the hint V-M, I appreciate your opinion. I calculated the piston-speed to 19m/s (3748ft/min) @ 7000rpm and from what I've read that should be ok? I would say at piston and rods is enough, but straithness should be checked from crank. Surely balancing crank + flywheel (+ pressure plate) gives bit more insurance. In my knowledge 19-20 is max. readings? I think formula 1 and other real race engines are 25 max. in 7500rpm its 20.4 m/s, so what I'm saying is at u can go to that 7000 rpm but not for longer periods with current (original) piston + rod weights. Moving mass is realy big on this N9T. The most heaviest parts which I have found from any gasoline engine... only diesel engine parts have been heawier. Block it self is the most thick one which I ever seen on gasoline engine... same opinion did say this engine machinist who have been borring engine blocks for 40 years. IMHO I'm not usually looking those calculated things but surely those can be have some informatic content... V-M http://www.csgnetwork.com/pistonspeedcalc.html http://en.wikipedia.org/wiki/Mean_piston_speed Quote Link to comment Share on other sites More sharing options...
Johnny Posted January 15, 2008 Author Report Share Posted January 15, 2008 hehe, I forgot about this thread The block thickness sounds like a good thing to me, I assume that it should hold up for high hp then? To sum things up: Raising the rev-limit to 7000 rpm is fine if you balance the rods and pistons. (if the valve-springs give enough pressure.) Does anyone know any rules of thumb on seat-pressure vs rpm? Quote Link to comment Share on other sites More sharing options...
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