In a prior post, I suggested that one of the reasons 'chips' don't deliver the HP and Torque that's touted by the manufacturer is because a 'chip' should really be combined with an exhaust cam sprocket. The purpose of this post is to relate my understanding of (1) why this is so, (2) summarize relevant dyno results, (3) profile the possible performance gains in comparison to performance of the 540i, and (4) illustrate likely costs. I don't presume to have it all right, however, and welcome corrections and suggestions by readers.
1) Why combine the two. When we buy a Dinan or Jim Conforti Chip we're trying to alter ignition and fuel in a way that renders a more powerful mix when the cylinder fires. Now that we've succeeded in doing this, there's a related question: How fast is the burnt or spent fuel in the cylinder dispersed or sucked away to make room for the next injection/burst of fuel. The answer involves the exhaust cam sproket because it determines the "overlap" period when both intake value (in comes the fuel) and outtake valve (out goes the exhaust) are operating. Relative to the stock exhaust cam on our M5s, a "sport" exhaust cam has a wider lobe and, as a result, keeps the exhaust value open longer. This, in turn is conducive to producing a broader power range. And specific to our M5 engines which are "Horsepower engines" (more HP than Torque), the sport cam sprocket helps generate more torque at lower rpms (which is what we really want). In short, a chip and exhaust cam sprokect are complements that work together, not individual, independent performance modificaitons.
2) Dyno results. You may have noticed that it's very difficult to get dyno results on both chip and exhaust cam sprocket. This is because only Dinan provides this information because ONLY Dinan makes an exhaust cam sprocket for our M5s. This is not the case, for example, for my 88M6 where a lot of replica cam sprockets exist, including a unit produced by Dinan. So, unfortunately, we can't discern from stats available how a Conforti chip or a Mark D'sylva chip combines with an exhaust cam sprocket. The only data we have for our M5s is for a Dinan chip and Dinan cam sprocket.
For our M5s, a Dinan chip claims a PEAK 37 HP gain at 7000 rpms and a PEAK 36lb/ft of Torque gain at 3500rpms. Add the exhaust cam sprocket, and Dinan claims a PEAK 54HP gain at 5500rpm and a PEAK 52lb/ft of Torque gain at 5000rpms. So instead of the M5s stock 311HP at 6800 rpms, the chip and cam sprocket generate about 350HP much lower down the rpm band, at 5000, and that's where we want it, lower down the rpm band. And instead of the stock 266ft/lbs of torque at 5000 rpms, the chip and cam sprocket deliver 293 ft/lbs at 4000 rpms and 318ft/lbs at 5000 rpms.
3) Chipped and cammed M5 vs. 540i. I make this comparison because the 540i is part of the 5 series family and is also a 4 door, both weighing in at around 3800lbs. As I said in my prior post on "Appeal of a 4.10 differential", BMW is evolving the 540i (since 1996) into a torque monster relative to our M5. Stock TQ in the post 96- 540i is around 330 ft/lbs at 4000 rpms -- exactly where one wants it if 0-60 acceleration is a concern -- and yet the 540i has only a 282 HP engine. In short, it's a torque engine vs. our HP engine.
Ok, the comparisons I'm going to make now have our M5 with chip and cam sprocket vs. a stock 96 and then 98+ 540i. This may not seem fair, but a chip doesn't do a lot for these later 540is because they are already pretty efficient (ie., a chip increases HP and TQ only 10 points) and there is no exhaust cam sprocket for them.
So, at 4000 rpms our stock M5 produced 262 ft/lbs of torque vs. 288 for the 93-95 540i, 330 for the 96-98 540i, and 332 for the 98-2001 540i. With chip and cam sprocket, our M5 increases to 293 ft/lbs at 4000. Better news is that at 5000 rpms, our stock M5 produces only 266 f/lbs of torque vs. 307 for the 93-95 540i, 295 for the 96-98, and 297 for the 98-2001. With chip and cam, our M5 generates 318 ft/lbs of torque at 5000 rpms, exceeding all the later 540i models. And by 6000 rpm, our stock M5 torque goes from 263 ft/lbs vs. 243-245 for the post 96 540i's, whereas with chip and cam our M5 produces 306 ft/lbs.
With these increases, I have no doubt that our M5's 0-60 performance would improve considerably, but may still not match the 6 shift 540i (which is faster), whereas we'd easily beat the 540i in the 1/4 mile sprint. But, as I said in my other post, if we really want winning accelerating on all fronts (from 0-60) we'd have to make better use all that increased chip and cam power by replacing our current 3.91 or 3.73 rear differential with a 4.10. And, though costly and rare, there is a supplier who will custom make one for us (see my post on the 4.10 differential).
4) Cost and Installation: Again a comparison might be useful. For my 88M6 a conforti chip costs around $250 and I can find an exaust cam sprocket (not by Dinan) for around $125. Dinan's cam for my M6 is about $250. Installation is 5hrs (say $400) and if/when you do it, good time to replace your timing belt because they're all connected to the same pullies in the same area of the engine. For the E34M5, same price for the chip, but Dinan has a monopoly on the cam sprocket. Cost is $561 and 6 hrs. (figure $450) to install. By the way, no problem mixing, say, a Jim Conforti Chip with a Dinan Cam Sprocket -- they are compatible.
Finally, let me say there's a nice little mini survey of chip owners in a hidden section in the BMW Enthusiast's Companion, pp. 258 that says while most chip owners were satisfied and some were not, those chip owners who also had a cam sprocket "were a very happy bunch".
Hope this information is of some value. Welcome feedback. Cheers.
Samson
Good info,
I agree with you on sprocket and chip both together (I got mine from Korman) but have since tried three different chips to find the best combo, (I worked at a shop that had a dyno ) and the difference was about 6hp to 10 hp
Torque all so increased but I have since lost all the data and have change jobs (sorry guys)
Was I happy when I changed the sprocket and chip YES I recommend it to everyone
All so I have just rebuilt another engine and fitted two Schrick cams (with slandered sprocket)
I have only done 500 km keep you posted on the performance
Question- Has anyone fitted cams and all so changed the sprocket
Originally posted by samson ...and Dinan claims a PEAK 54HP gain at 5500rpm and a PEAK 52lb/ft of Torque gain at 5000rpms. So instead of the M5s stock 311HP at 6800 rpms, the chip and cam sprocket generate about 350HP much lower down the rpm band, at 5000...
I dont think this is what is meant by the claim.
When they claim 54hp gain at 5500rpm, they dont mean 54hp + the stock max. hp of 311 (wich is at ~6800rpm).
What i belive they mean is that HP figures are improved differently thruout the rpm range, and at 5500 is the peak improvement of 54hp, compared to stock power at 5500rpm.
If this was my car in question, take a look at this stock dyno print, and you can see that my engine has aprox. 251hp (185kw) at 5500rpm, and what Dinan claims is that here i would have aprox. 305hp (251 + 54).
What i would gain at max. Hp rpm (wich on my engine is at the rev limiter), they make no claims about.
This is not something i know for a fact, but i belive this is what is meant by the claim stated by Dinan.
Dont you guys aggree on this?
For the record my car is a 3,6L, and now also have the Mark D'Sylva chip installed.
Yes, the claims are of the max hp generated at any point along the powerband. 54hp is still very significant though at any spot.
Regarding Samson's thought about exhaust cam sprocket and chip, I will try to critique it not criticise it.
The chips do not really make the cylinder fire more powerful. They alter the spark and fuel timing so that the spark ignites at an earlier time, advance. During the normal 4-stroke combustion cycle, the spark actually ignites before the pistons reach top dead center. This is so because fuel takes some time to burn. So with the tuners merely adjust the spark and fuel for this. This is why you have to use a higher octane gas for cars that normally use below 91 octane. Higher octane gas doesn't have more energy in it. The higher the octane, the longer it takes for the fuel to burn.
Using a cam gear is almost the same as having vanos in the engine. A vanos unit from the M50tu and S50 engine adjusts the exhaust cam so that it has more or less valve overlap. When compared to non vanos M50 engines, the vanos ones don't necessarily make more power. However, their torque is much lower in the powerband, making the engine more usable throughout the rpm range.
When comparing the M5 to the e39 540i, all I have to say is that I have both, sort of. My car is lighter than a 540i so my results could be different than yours. Look at my thread "An S38 in a 525i." http://www.bmwm5.com/vbulletin/showt...threadid=21821
I really liked your post. I am planning on getting a cam gear someday, maybe the one from the 3.8L so that it would compliment my D'Sylva chip well.
Originally posted by Mark J ...Higher octane gas doesn't have more energy in it.
~Correct
It could have more, it could have less, the Octane rating does not relate to "burn energy" (BTU) in the fuel. it tells how much compression/heat the fuel can withstand without selfigniting.
Quote:
The higher the octane, the longer it takes for the fuel to burn.
Here i have to disaggree.
The Octane rating does not relate to the flamefronts speed (how fast it burns), the high Octane fuel could have slower or faster flamefront compared to low Octane fuel.
The Octane rating only tells the compression/heat rating of the fuel.
This is a very common mistake
[/b][/quote]
Originally posted by Mark J Thanks. I guess I stand corrected. Then why do we have to use higher octane gasoline for advanced tuned chips?
Mark J
Not corrected, but informed
You actually posted part of the reason for needing higher octane rating when using performance chips, in your previos post in this thread. (if i understand it correctly).
Imagine this:
lets say a stock chip ignites the sparkplug at 10degrees Before Top Dead Center (BTDC), then we have the fuel ignited BTDC, but only part of it as it will burn from the point of the sparkplug, towards the outer edge of the bore, but in the time it takes the piston to reach Top Dead Center (TDC), only a small part of the fuel around the sparkplug is actually ignited.
This part of the fuel that is ignited expands, and creates extra compression in the rest of the compression chamber.
If this amount of compression gets to high for the fuel used, the part of the fuel that is not yet ignited, will selfignite and cause way too much pressure in the compression chamber (this is the pinging that can be heard by us, and felt by a knock-sensor).
Then, if one uses a performance chip that (lets say) ignites the sparkplug at 2degrees earlier than the stock chip, the flamfront (the front of the ignited part of fuel) that comes from the sparkplug, and expands out towards the outer edge of the bore will have travelled further when TDC is reached, and have created more compression of the still un-ignited fuel.
Then if one uses a higher Octane rating fuel (can withstand higher compression without selfigniting), this higher compression of the still un-ignited fuel is no longer a problem that causes pinging, and it is possible to have more compression power to push down the piston.
And, this is why racecars use speciel racefuel that have a faster travelling flamefront (more compression to push down piston), and high Octane (ex. 107 Octane, for withstanding this higher compression of un-ignited fuel).
Hope this is an understandable explanation (it is the best i can come up with @ 1:35Am )
__________________
Mvh. Finn Donati
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Last edited by Donati; 8th September 2002 at 03:00.
Many thanks to you all , especially Donati, Mark J and g,boyd for your corrections, critique, and suggestions. The clarifications on the role of the chip and ignition were very illuminating to me and I certainly stand corrected on this dimension.
Regarding how to interpret Dinan HP and TQ gains, I also agree with the clarifications offered. Dinan is not saying the result of a chip and exhaust cam sprocket on the E34M5 is 311 stock HP plus another 54 HP at peak gain = 365HP overall. I know this, yet not being clear about it when relating findings means the clarity tends not to be 'up front' in my thinking, and thus confusing to others.
Anyway, the correct interpretation goes thus;
-- Stock peak HP on the E34M5 is 311 at 6800 rpms, whereas peak HP gain with chip and cam is 53HP which takes place at 5500rpms. Therefore, this raises the stock HP at 5500 rpms from 273 to 326. Still impressive, largely because that additional 50 HP becomes available 1300 rpms earlier under full throttle. In addition, HP keeps rising to about 350HP, on average, from 5500rpms to 6800rpms, resulting in an increase of 35HP at 6800rpms which we can add to stock 311HP at 6800.
-- Stock peak Torque on theE34M5 is 266 ft/lbs at 5000 rpms, but in this case peak TQ gain with chip and cam of 52ft/lbs also occurs at 5000rpms. This raises the stock TQ at 5000rpms from 266 to a more heafty 318ftlbs. That's very nice.
-- Also, note the combined chip and cam raise TQ 42 ft/lbs at only 2000rpms, raising stock TQ from 205 to 247. Again, impressive from the viewpoint of getting more power when we hit the throttle.
Mark J
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