Who had his 308 2v or 4v on the dyno and can tell about real figures. It is said that the early 308's had 255 Bhp with carbs. The quatro valvole's had their more realistic 240bhp. (but still) The lighter Fiberglasses was displayed at his introduction in Auto&Motorsport with a honest 227 BHp and a claimed 254 km/h My Fiberglass drives convincingly away from a 328 and even from a 348 but shows 224 bhp at 6500 rpm on the dyno and has a close ratio gearbox wich only allows an easy 225 before red line appears and the right foot needs to be lift. So, who is kidding who? Off course it's easy to switch over to a dynoreport without adding losses. I discovered that the ferrari factory comfortable forgot to mension this and that's exactly why I wonder who had experiances with or on the dyno. I also discovered dat most 308I's deliver about 190 bhp and 235 was top for a quatrovalvole. Gives you a nice thing to think about. At the other hand, it won't take away my pleasure to drive these beautiful old cars. Marcel
The only way to know is to dyno it on an engine dyno, too many factors to take into consideration and too much guessing otherwise. Using a chassis dyno and guessing at the drivetrain losses is inaccurate. People here seem to think 20% is acceptable but this is also to the owners benefit to make the HP figures meet their expectations. 15% is realistic but it makes people sad that the car doesnt make what ferrari claims they do so 20% is used and the smile returns. A tweeked out GT4 308 engine made 235HP I believe and that was euro configuration. Drysump will not add 20hp to a stationary engine so 255 is a crock.
FChat sponsor Carobu has some Ferrari engine dynos on their site - www.carobu.com - and an absolutely tweaked out Euro GT/4 makes about 235 SAE or so as mentioned. It was common in their contemporary times to assume Ferrari lied about hp on ALL of their cars by 10 - 15%. Look at some of the V-12 engine dynos on Carobus site - it's very interesting. I think the later cars' factory specs are much closer to reality. While rear wheel dynos are not exactly comparable across cars for engine output (too many variables - tire friction, etc), most of us that do these use a 17% loss factor on transverse engine V-8s to give an approximation of flywheel hp. All that said, the best use of any rear wheel dyno is tuning changes on the same car. If anyone has other engine dynos, I'd be interested. Hey Mods - Could we start a sticky thread just for dynos?
Thanks guy's ! I would have responded earlier but there was an error. It's true, what you all said. And in my opinion it's far more important to use dyno-figures as a way to improve adjustments and actually see what works or not. For instance, there was a difference of almost 7 bhp loss after I removed the airinlethose and warm air was sucked in.This is significant and has convinced me how usefull the original airintake is. An internal sportreplacementfilter is good but to change the whole set up for four hot airsuckers would be desastrous. I enclose a pic of a run with the airboxlid removed. It would be complementary indeed to have a seperate tread for dyno results, that's a very good idea. I would be most interested in the findings of other DIY's. For instance, in my opinion there's a lot to win with higher compression pistons because of the existing overlapcaracter. I discovered that, to keep my engine reving in it's optimal range, I should stay between roughly 5000-7100 rpm. On the street this will be unacceptable in my opinion. With the standard compressionratio changed up to 10.5 there would be a lot to win I guess. But I wonder who has some experience with this in a carb'd setup. Ignitiontiming and enrichment are obvious players in this game. Hopefully some one can enlighten me. Regards, Marcel Image Unavailable, Please Login
FYI, this is a baseline dyno (unmodified, except for addition of big high flow cats, no mufflers) 85 euro QV. 243 SAE HP (@ the crank w/ 17% loss) Image Unavailable, Please Login
Thanks Luigi, This was the powercurve of my '76 2V from last friday. These two runs show difference in ignitionadvance and I had changed stationairy jets from 30 to 35 for better takeover in 3500-4000 range. I have two "seetrough" silencers with almost no restriction and a K&N replacement filter. Regards Marcel Image Unavailable, Please Login
I hope you can read it. I thought, it would also be interresting to show the pre-stadium of the A/F R. I've managed to find a nice compromise in the change from 30 to 35. The takeover-gap is almost gone. Guess 38 would be even better but will be far to rich at stationairy.
view on the silencers. The noise is acceptable. (for me it's rather like music) Image Unavailable, Please Login
Marcel graciously provided a copy of his dyno which I have re-sized here. There is a footnote on the original that there is NO correction factor ( i.e., this is raw rear wheel hp, not DIN or SAE corrected) with recorded ambient temp of 39.7 - 39.9 and a pressure of 1003.5 - 1004.3 during the run. To repeat what has been said before, it would be highly inaccurate to use this graph to directly compare with other cars, but this graph is very good for tuning and showing changes on the same car, which is what Marcel has done so well here. I do believe Marcel means he went from a 130 main to 135 main jet size. His experience in going to a larger main jet mirrors my own dyno tuning with the approximate entire curve shifting about a point or a little better in A/F ratio for each change of 005 (e.g. 130 to 135). The take-over gap he mentions as most know is the shift from idle/transition to main circuit, which as we have discussed in other threads shows the bringing in of the main circuit earlier with the larger main jet. Many American cars seem to like 140 mains in my experience. Excellent work, Marcel, and many thanks for sharing your information. Image Unavailable, Please Login
Thanks Russ for your perfect explaination. you've made my point. (that's my problem with being a Dutchman) The 140 is explainable because of the fact that European gasoline contains less ethanol. We (still) have 3%. I worry about the comming years because they are thinking about 10%. For the owners of carb'd cars this is a real point of future attention. Best, Marcel
What is the effects of the Ethanol? Not much of it in the petrol in OZ. Our high octane pump fuels hit 98. There is one new fuel that is rated @ 100 and includes 5% ethanol. I run a Alfa 105GTV track car on it and it runs fine.
To my knowledge, ethanol further 'lightens' a fuel causing our carb'd cars to require more fuel ie larger jets to balance out the misture. Mike at pierce manifolds told me that fuel now compared to about 30 years ago in the US requires about a 15% change in jet/ ac jet sizes to make them run as they were designed to.
I have tried the usual places to find a set of carbs and cant find them,Please point me to manifolds and carbs. Im ready to get out the hole saw and bolt a holley to the top of the manifold.
I just sold an entire set of NOS webbers and manifolds I had sourced a 1yr ago. try Lyle at ferrari parts exchange, he sourced mine. took about 3months but he came thru.
For carbs, I am using a set of commonly available Weber 40DCNF-12s which work well ( the Mondial qv Weber conversion is well documented on FChat) when easily re-jetted. I got mine at GT Auto Parts in Arizona, but the -12 is available from most Weber shops such as Pierce Manifolds (www.piercemanifolds), VW hot rod shops, as well as coming up on Ebay. The carb manifolds (I assume you mean for a a V-8 qv) are a bit more tricky. Modena Engineering in Australia used to make them (that's what we used) or they can be fabricated by most good welders from stock. The 2 valve manifolds will not fit your qv heads. Good luck!
Sorry for delay but Europe is'nt quite having the same timescedule. Let me try to explane. The octane in the fuelmixture will affect burnrate. It's stoichometric value ( the optimal burnrate) changes with suplementing octane wich leaves you with a leaner mixture. With a motormanagement you're engine enriches and changes ignitiontiming. This is acceptable within range. (10-15%) The newest engines with staged directport injection can cope with much higher octane rates because they give injectorpulses at different timing wich starts already in a early compression buildup and are set for the near future. The older carb'd engines have no management that prevents them for overheating. They have just one setting that can only be changed by rejetting and change ignitiontiming manually. Here in Europe, we will have to take serious measures when increases from 3% to 10% octane in our fuel find there way in our fueltanks. Ironically the only way to keep up is to enrichen the setting wich leaves no serious gain for enviroment at all in my opinion. Best, Marcel
I fear there may be some misunderstanding in the relationship of Ethanol in fuel to octane, burn rates and stoichiometric A/F ratios. Ethanol is a high octane fuel, which makes it more resistant to pre-ignition, meaning you COULD advance your timing to take advantage of this and get more power. In practice, it's been my experience that most flex-fuel vehicles that can run on pure gasoline or E85 don't implement this. I've been out of that end of the business for 3 or 4 years now so hopefully manufacturers are taking advantage of this now. Alcohol (methanol or ethanol) doesn't have the energy density of gasoline, so you need to introduce a lot more of it into the cylinder than with gasoline. Stoich on gas is ~14.6:1, where ethanol is something in the 9's. Running E85 requires that you put in about 20% more fuel than gasoline. Using E10 is only, if I recall, about 2.5% different in A/F ratio. In other words, you'd need to increase your fuel supply, via jets or whatnot, by 2.5% to run on E10 vs gasoline.
Thanks, you've read it, In my last line I ment ethanol instead of octane. I should have checked my tekst.
