Hot Wire conversion
- Thread starter BCOSTELL
- Start date
Hi.
I have between 15 to 20bhp as done with my car. It had the MBE conversion done in '97 by Bob Watson Engineering which included replacement of ECU (under passenger seat)distributor, all new sensors (993 I believe), loom swap, SSI heat exchangers, removal of hot air pipes/fan motor. Colin Belton of 9M - the 'ninemeister' mentioned he had an MBE on the shelf. The Motec unit is current favourite, also speak to Colin or Bob. If you are interested I'll send along some pictures of the revised engine bay (much tidier) and the '97 costs (astronomic).
Best regards,
Chris
I have between 15 to 20bhp as done with my car. It had the MBE conversion done in '97 by Bob Watson Engineering which included replacement of ECU (under passenger seat)distributor, all new sensors (993 I believe), loom swap, SSI heat exchangers, removal of hot air pipes/fan motor. Colin Belton of 9M - the 'ninemeister' mentioned he had an MBE on the shelf. The Motec unit is current favourite, also speak to Colin or Bob. If you are interested I'll send along some pictures of the revised engine bay (much tidier) and the '97 costs (astronomic).
Best regards,
Chris
Guest
New member
964 AFM is the same as the 3.2 (I have one in my car), so no performance increase there. 9M reckons the 964 AFM and throttle body offer no significant restriction up to about 310bhp (IIRC).
993 is hot film (isn't it?).
The results of the hot film conversion are subject to some debate. Mike58 gained (IIRC) 12hp on the dyno from this. He later remapped and tweeked exhaust plus bigger throttle body and found (IIRC) 4-5hp more, though his midrange gains in hp/torque were I think more impressive (this may have been seat of the pants stuff but it was a while since we discussed this stuff).
If you look at the thread on the 3.2 dyno day from 20 August, you will see another 3.2 with FVD hot film kit, ECU upgrade and SSIs that made 248hp.
The best summary description I have seen was from a US 3.4 owner who described the hot film kit as the last thing he would do after doing everything else - ie exhaust, cams, intake manifold, displacement. He also described it as the icing on the cake and his dyno tests showed only 5hp gain on a fairly well modified engine. This ties in with the results from 9M, who use the std AFM and 964 plastic intake then go to ITBs completely bypassing the hot film option (I think).
HTH
Richard
Edit - It might be useful to know your goals in terms of expected hp and your budget
993 is hot film (isn't it?).
The results of the hot film conversion are subject to some debate. Mike58 gained (IIRC) 12hp on the dyno from this. He later remapped and tweeked exhaust plus bigger throttle body and found (IIRC) 4-5hp more, though his midrange gains in hp/torque were I think more impressive (this may have been seat of the pants stuff but it was a while since we discussed this stuff).
If you look at the thread on the 3.2 dyno day from 20 August, you will see another 3.2 with FVD hot film kit, ECU upgrade and SSIs that made 248hp.
The best summary description I have seen was from a US 3.4 owner who described the hot film kit as the last thing he would do after doing everything else - ie exhaust, cams, intake manifold, displacement. He also described it as the icing on the cake and his dyno tests showed only 5hp gain on a fairly well modified engine. This ties in with the results from 9M, who use the std AFM and 964 plastic intake then go to ITBs completely bypassing the hot film option (I think).
HTH
Richard
Edit - It might be useful to know your goals in terms of expected hp and your budget
Oh ROUGE OH ROUGE,
Some day maybe , You have changed the mirrors and that looks excellent
Have you lowered yours, its sits very well,
Any changes that you made that you would recommend, and also those that you wouldn't
By the way what was the max speed after L'Eau Rouge that you got to?
Thanks
Brian
Some day maybe , You have changed the mirrors and that looks excellent
Have you lowered yours, its sits very well,
Any changes that you made that you would recommend, and also those that you wouldn't
By the way what was the max speed after L'Eau Rouge that you got to?
Thanks
Brian
Guest
New member
Spa May 05 for me, doesn't look like the same day.
My car has had a lot done to it. Highlights include 7/9x16 Fuchs, 22/29mm torsion bars, Bilstein dampers, 22mm adjustable rear ARB, polybronze bushes, 964 brakes, semi-lightweight G50, rebuilt 260hp 3.2 with all the good bits including 993 Supercup cams, SSIs and LW muffler, backdate heat, LW interior with race buckets and no sound deadening. Yes, its much lower than std, particularly the front on 225/45s - see below
I can't recall the top speed post Eau Rouge but I was into 5th so safely 125+mph. This was on a new engine that was not healthy and was making only circa 240hp. It was so new I ran it in on the way to Spa and then limited my revs for 1.5 of the 2 days. Towards the end I was touching 6500rpm at times whereas now its a 6900rpm screamer all the time. Needless to say, we found some problems when it was pulled apart for the second time. Looking forward to Spa next May with a properly sorted, lighter, faster car.
My car has had a lot done to it. Highlights include 7/9x16 Fuchs, 22/29mm torsion bars, Bilstein dampers, 22mm adjustable rear ARB, polybronze bushes, 964 brakes, semi-lightweight G50, rebuilt 260hp 3.2 with all the good bits including 993 Supercup cams, SSIs and LW muffler, backdate heat, LW interior with race buckets and no sound deadening. Yes, its much lower than std, particularly the front on 225/45s - see below
I can't recall the top speed post Eau Rouge but I was into 5th so safely 125+mph. This was on a new engine that was not healthy and was making only circa 240hp. It was so new I ran it in on the way to Spa and then limited my revs for 1.5 of the 2 days. Towards the end I was touching 6500rpm at times whereas now its a 6900rpm screamer all the time. Needless to say, we found some problems when it was pulled apart for the second time. Looking forward to Spa next May with a properly sorted, lighter, faster car.
Stunning looking Car Richard
and some of what you have gone through are the direction I want to go in.
I only have the car a year and my mind is constantly building a longer and longer build list.
Interested to hear how you find the handling after lowering on Bilsteins, how much of a compromise is it, its not until your on track that the little roll that there is starts affecting the handling, but I don't want to so too far in lowering to having my spine smashed at every man hole
The Torsion bar measurements ie 22/29 mm
is this an larger diameter torsion insert, or did you adjust the standard car to lower it.
Do you know anyone that has gone to 17 inch diameter wheels on 3.2, how much of a difference is there......
You are probably fed up answering these types of questions, did you keep a log of the changes to the car.
I would love to read the full spec.
bcostell@gmail.com
and some of what you have gone through are the direction I want to go in.
I only have the car a year and my mind is constantly building a longer and longer build list.
Interested to hear how you find the handling after lowering on Bilsteins, how much of a compromise is it, its not until your on track that the little roll that there is starts affecting the handling, but I don't want to so too far in lowering to having my spine smashed at every man hole
The Torsion bar measurements ie 22/29 mm
is this an larger diameter torsion insert, or did you adjust the standard car to lower it.
Do you know anyone that has gone to 17 inch diameter wheels on 3.2, how much of a difference is there......
You are probably fed up answering these types of questions, did you keep a log of the changes to the car.
I would love to read the full spec.
bcostell@gmail.com
Guest
New member
Most of the stuff I have done to the car is on this forum if you search. I have a very big folder of bills but no log as such. Its a good fun little track car with its current set-up but its still quite some way from optimum - even without changing components. Its pleasant enough to drive on the road (though very loud). Many people have commented on the change in ride when going to larger torsion bars. Its firmer, yes, but not harsher. The shocks are really what has the greatest effect on ride quality.
The 22/29mm measurement is the effective diameter of the torsion bars. Standard is 19/24mm. The spring rate of the bar increases to the 3rd power of the diameter, so I have increased the spring rates quite a lot, though it is still a fraction less than a 964RS and a good deal less than a 964 Cup, for example.
Plenty of people use 17s on 3.2s. In itself, an increase of one inch in wheel diameter will do nothing other than shorten the sidewalls slightly - assuming the overall diameter and rolling circumference remain the same. Some guys like Andy Tims have tried 17s and gone back to 15s in order to get the gearing advantage that a smaller overall diameter gives. I tried it as well and couldn't really pick the difference between 15s and 16s, so I went back to 16s on which I could run 225/245 tyres rather than 205/225 I had on the 15s. I personally think the wider rubber - particularly at the front - makes more of a difference to lap times than the gearing, though it depends on tracks. A 245/45x16 is also fractionally shorter than a 225/50x16, though not as short as a 225/50x15. Some years ago, I did some testing with a friends 2.4 911E race car comparing 205/50 and 225/50 rear tyres on different tracks and we found that there was enough difference to make it worthwhile swapping from one set-up to the other for different tracks.
The main benefit in using 17s is the greater access to more track tyres. Track tyres usually have a much stiffer sidewall than road tyres, so the shorter sidewall of 17 inch tyres is not a huge benefit. If you have wide enough rims, you can get up to 245/275 tyres under the narrow body and 16s simply don't come in those widths with the right profiles. There is not much left in 15 inch sizes and 16s are going the same way. For the time being I can get 225/50 and 245/45 sets for 16s but I can't get a 225/45 / 245/45 combo and I am restricted to 3 brands - Yoko AO48Rs (expensive noisy and slow), Michelin Cups (expensive, quick on medium/heavy cars, long wearing) and Kumho V710s (cheaper, quick and long wearing). Going to 17s adds Pirellis, Toyos, Avons, Dunlops and maybe others to that list.
The other thing to consider is the unsprung weight and strength of the wheel. Fuchs wheels are light and strong and will not break because they are forged wheels. The Porsche OE Cup wheels that are popular are alos a good wheel but the offsets are wrong for a pre-89 911 and big spacers are required (1 and 2 inch front/rear, I think). The Cup replicas are heavy and are not as strong. There are quite a scary number of failures of these wheels on track.
If you are thinking of modifying your car, then it helps to have a pretty detailed plan. You have two main choices. Do the whole lot at once - expensive but ultimately cheaper as you don't repeat anything - or, do it in stages, so you can grow with the ar and plan one project at a time. Even that choice depends to a large extent on what your end goal is - fast road car, occasional track days, nothing but track days and I want to hang on to the back of the GT3s! for example. Why not start a new thread here and float your ideas so you can get feedback. You may decide its cheaper or easier to just buy a new car. I am not a real expert, but I have written a few cheques to guys who are, so I have picked up a thing or two. Happy to help in way I can.
Richard
Correct me if I am wrong, but the benefit of swapping the Air Flow Meter for say the hot wire setup is that it will work with any camshafts you fit in the engines. Big cams confuse the standard AFM by making pulses or something. Once you get the hot wire you can fit a longer duration cam with higher lift, a unrestricted exhaust and port around the valves in the head if you want to go that far. The rod bolts would also need to be upgraded for the extra RPM involved to ARP or Raceware. With all this, a remap and bigger injectors if required over 100bhp per litre should be achievable. Obviously the low end RPM will lose power and drivability. Maybe the throttle body would need to be enlarged or a whole new inlet manifold.
Guest
New member
Good point Nathan, one of the reasons you can't run really hot cams in a 3.2 is the flapper style AFM as the reversion upsets the AFM reading, but there is also a second. The std pistons have a high dome for combustion efficiency and emissions reasons. There is not enough valve clearance without machining valve pockets into the pistons for a really high lift cam. My 993 Supercup cams are about the best std grind you can do with the std pistons, though for race apps you can do a fraction more lift if you are happy with the reduced clearance and tolerance. So, why not swap pistons for an "S" style piston with big valve pockets, you may ask? You can, but as the bore of the cylinders increased as engine displacement increased over the years, you start you divide the combustion chamber in half and the off center spark struggles to produce a flame front quick enough to get right to the far side. The result is detonation. The fix is twin plug (or lower compression or higher octane fuel). The cost is getting exponential!
Even with very good or peaky cams - like Mod S or 906 grinds, for an example of good and peaky cams respectively - plus all the goodies to allow high revs, the std intake manifold won't flow enough air to get you past about 275hp (unless you are forced induction). So you will not get 100hp per litre. I am at 260hp and hoping the current chip will make 265-270hp when dyno tested and the best advice is that the intake manifold is now the hold-up. So the next step is a 964 inlet, good for probably ~325hp on 9Ms MOTEC+1 packages on 964 motors, but needing separate engine management to open the resonance flap, or throttle bodies, again requiring engine management for operation. Then the restriction in my engine is the cams/pistons and secondly the relatively narrow primaries of the SSIs extractors. For example, 9M had a 3.2 engine with big barrels and pistons displacing 3.5 litres and making 275hp. When they went to MOTEC and plastic 964 intake they got 300hp, which is fairly close to what they get from 964 motors equivalently tuned.
One thing I don't know is if hot film gets you past the intake reversion/pulse problem of big cams? It still depends on air flow over a hot wire, so does it solve the problem ? MOTEC etc that can run a combo of Alpha N/MAP certainly does.
RB
Even with very good or peaky cams - like Mod S or 906 grinds, for an example of good and peaky cams respectively - plus all the goodies to allow high revs, the std intake manifold won't flow enough air to get you past about 275hp (unless you are forced induction). So you will not get 100hp per litre. I am at 260hp and hoping the current chip will make 265-270hp when dyno tested and the best advice is that the intake manifold is now the hold-up. So the next step is a 964 inlet, good for probably ~325hp on 9Ms MOTEC+1 packages on 964 motors, but needing separate engine management to open the resonance flap, or throttle bodies, again requiring engine management for operation. Then the restriction in my engine is the cams/pistons and secondly the relatively narrow primaries of the SSIs extractors. For example, 9M had a 3.2 engine with big barrels and pistons displacing 3.5 litres and making 275hp. When they went to MOTEC and plastic 964 intake they got 300hp, which is fairly close to what they get from 964 motors equivalently tuned.
One thing I don't know is if hot film gets you past the intake reversion/pulse problem of big cams? It still depends on air flow over a hot wire, so does it solve the problem ? MOTEC etc that can run a combo of Alpha N/MAP certainly does.
RB
Thanks for the great bhp no's.
I'm sure the hot film would be ok with any cams.
I bit the bullet, bought a 930 with a G50 gearbox in it. I am upping it to near 400bhp. It doesnt weigh much more than my 3.2 as it has f/glass bumpers and engine cover.
I'm sure the hot film would be ok with any cams.
I bit the bullet, bought a 930 with a G50 gearbox in it. I am upping it to near 400bhp. It doesnt weigh much more than my 3.2 as it has f/glass bumpers and engine cover.
Posts made and opinions expressed are those of the individual forum members
Use of the Forum is subject to the Terms and Conditions
