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Don1
8,974 posts
77 months
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No, only the head has changed (but you're perfectly correct about the ECU!). Everything else is still standard (OK, no cats, and a different exhaust & airbox), but pistons, bottom end and everything else is standard. But I agree, the more tuned an engine is, the more 'undrivable' it is. I'm not saying the S6 is the be-all and end-all of engine design, but it does look like the engine will take over 430bhp before starting to change cams/VCT etc to prove your point. 
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spitfire4v8
Original Poster
1,305 posts
50 months
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Well here it is .. time to stop (for the moment) This is the last run with the modified airbox (short inlets) overlaid over the previous best graph. Finally broke the 380hp mark (317 at the wheels for those who like wheels figures). As you can see the graphs exactly overlay until the top end where the airbox starts to just show an improvement. The total gain over the car as delivered is just short of 30bhp. It's worth pointing out that this was a secondhand engine that then did a season of hard racing and hasn't been touched internally since. 
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RedSpike66
1,968 posts
81 months
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Don1 said: No, only the head has changed (but you're perfectly correct about the ECU!). Everything else is still standard (OK, no cats, and a different exhaust & airbox), but pistons, bottom end and everything else is standard. But I agree, the more tuned an engine is, the more 'undrivable' it is. I'm not saying the S6 is the be-all and end-all of engine design, but it does look like the engine will take over 430bhp before starting to change cams/VCT etc to prove your point. Don I think the FFF head has a very different cam profile to standard iirc, and that's why VVT is going to make a big difference...
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Don1
8,974 posts
77 months
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Really? That embarrassing! 
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clive f
6,701 posts
102 months
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nice work Joolz 
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Ant.
4,903 posts
150 months
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Very interesting Joo, as soon as the Griff sells, I think I need to visit you......
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RedSpike66
1,968 posts
81 months
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Don1 said: Really? That embarrassing! That's ok... You're an expert in a different field 
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dpd3047
215 posts
35 months
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Look at the cam lobes on the FFF head you will see that the lobe is semetrical, the acceleration and deceleration ramps are the same thats why they have to run a lot of lift and duration to make power hence VVT to make it drivable, now look at the standard type TVR cam they are assemetrical the inlet ramp is fast opening and slow closing the exhaust lobe is slow opening and fast closing thats why it uses finger followers this gives fast valve acceleration and using the correct shape follower makes using high lift cams drivable.If you look at the first FFF heads they were ported but they used near standard camshaft with semetrical lobes because of the bucket tappets and it only made same power as a good 4 litre S engine, the 3.6 is well capable of making 400 BHP with some decent profile cams, i run a virtual dyno test program ive tested a lot of profiles, also larger capacities, and ported heads on the S6.
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dvs_dave
3,573 posts
94 months
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dpd3047 said: Look at the cam lobes on the FFF head and you will see that the lobe are symmetrical. The acceleration and deceleration ramps are the same which is why they have to run a lot of lift and duration to make the required power. However this is detrimental to drivability which is why VVT is being developed; to gain back the drivability lost by the altered cam profiles.
In comparison, the standard TVR cams have an asymmetrical profile. The inlet ramp is fast opening and slow closing, whilst the exhaust lobe is slow opening and fast closing. Finger followers are used because they allow for fast valve acceleration, and make using high lift cams more drivable.
The first FFF heads were ported but used a camshaft with symmetrical lobes because of the bucket tappets. In this form it was similar in performance to a standard 4 litre S engine.
The 3.6 is well capable of making 400 BHP with some decent cams. I run a virtual dyno test program, and I've tested a lot of profiles, larger capacities, and ported heads on the S6.
Hate to do this but......grammatically edited (hopefully correctly) for clarity.
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ceejay
1,220 posts
123 months
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I had a look at all of the graphs on Tuesday and the gains are very impressive. It's not just the bhp figure (up about 25bhp) but the torque curve is vastly improved which is now pretty similar to a 4L engine. We have some good logger data from the T350R at Oulton and Rockingham so we'll take the car there to how the bhp / torque gains translate to on-track performance. For comparison the 3.8 Wilder made 381.3bhp and 286lb ft in the car.
Given the engine has done a seasons hard racing and had lost 11 bhp from its original baseline figure, I'd say that with a rebuild and some total seal rings 400bhp would definitley be a realistic target with Joos new setup.
ceejay
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Zippee
9,452 posts
103 months
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Mime ran 366.9 at a rolling road day last year at Hilton & Moss on a dyno dynamics roller. Obviously I know different rollers can under/over read but still doesn't look too bad Standard though bottom end rebuild back in 2008, also running a De-cat chip along with full de-cats.
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dpd3047
215 posts
35 months
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As far as the rolling road debacle goes i think it fare to say that wheel figures are the ones to go by, as long as the road is set up correctly there should be no BS factor on losses ect, i will say this again the the standard factory engine outputs were 3.6 is 335 bhp @
7000 rpm the 4.0 is 342 @ 6500 rpm and the RR and S engines are 358 BHP @ 6800 rpm that is with cats. and in my opinion if you`ve got any TVR that makes 345 BHP @ the wheels i would say that that is a genuine
400 BHP @ flywheel this only apply`s steady state dyno`s.
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RedSpike66
1,968 posts
81 months
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Surely the losses should be (give or take a couple of percent) the same for all the recent factory-issued unmodified cars - same flywheel, clutch, gearbox, propshaft, diff, driveshaft etc and so at the wheels figure plus X bhp where X is always the same value gives you an accurate guestimate ??
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BCA
8,596 posts
126 months
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Very interesting, so 380bhp+ is possible... I look forward to seeing what you can do with a stronger base, perhaps the 400bhp NA 3.6 is very possible afterall. 
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s5tvr
1,216 posts
102 months
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BCA said: Very interesting, so 380bhp+ is possible... I look forward to seeing what you can do with a stronger base, perhaps the 400bhp NA 3.6 is very possible afterall. I don't know enough about the design and limitations of the SP6 engine but Porsche manage to get 440bhp out of their 3.6, so why not out of the SP6 ? I would imagine that the SP6 is probably capable of more but was never optimised at the factory as R&D would not have been commercially viable.
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spitfire4v8
Original Poster
1,305 posts
50 months
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I'm reasonably confident that I could see 400hp+ out of a 3.6 but I've not got the money to invest in it any further than what i've done so far. Anything else would have to be customer funded (with all the risks attached) or wait until I've made a little bit more money and can afford to throw a week at it all again.
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longone
216 posts
109 months
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Hi, just been looking at your plots and I notice the characteristic drop in output between 3-5000rev-1. Have any of you investigated what's causing it? I'm interested in particular because an engine (duratec I4) I've had built has a similar flat spot on its dyno plots and I've asked them to tune it out out. They are expecting inlet tract mods will sort it.
Colin.
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spitfire4v8
Original Poster
1,305 posts
50 months
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I think it's primarily a function of inlet tract length. Certainly the SP6 engines all exhibit that same torque curve trend even with different cam timing .. but when I did my inlet length comparisons the longer lengths produced a more normal looking curve, but killed the top end power when the lengths went very long.
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Basil Brush
3,858 posts
132 months
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s5tvr said: I don't know enough about the design and limitations of the SP6 engine but Porsche manage to get 440bhp out of their 3.6, so why not out of the SP6 ? I would imagine that the SP6 is probably capable of more but was never optimised at the factory as R&D would not have been commercially viable. Assuming you mean the GT3, I thought the 3.6 was around 415 with the 440 being the 3.8? Having VVT and variable intakes I guess avoids the single compromise setup the S6 needs so it can be optimised across the rev range. Being able to rev to 8.5k must help too.
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RedSpike66
1,968 posts
81 months
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Basil Brush said: s5tvr said: I don't know enough about the design and limitations of the SP6 engine but Porsche manage to get 440bhp out of their 3.6, so why not out of the SP6 ? I would imagine that the SP6 is probably capable of more but was never optimised at the factory as R&D would not have been commercially viable. Assuming you mean the GT3, I thought the 3.6 was around 415 with the 440 being the 3.8? Having VVT and variable intakes I guess avoids the single compromise setup the S6 needs so it can be optimised across the rev range. Being able to rev to 8.5k must help too. Porsche published figures currently.... | Engine | Bhp | Torque | | 3.4 | 330 | 272 | | 3.6 | 345 | 287 | | 3.8 | 385 | 309 | | 3.8GTS | 408 | 309 | | 4.0GT3 | 500 | 339 | Standard road cars, not specials, and only a few £billion R&D budget Looks like the 3.6 SpeedSix does quite well in comparison....
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