Quick Reference Guide for BMW 745i (E23) Tuning Options
Partly u pdated: 08.04.2008

I am preparing this summary to give some ideas how to tune the beast. Hopefully it also gives some answers to all of you who have sent questions about tuning options to the 745i.
The power/boost levels are approximate. Allow +-10% depending on e.g. engine condition.  It is a bit difficult to define exactly what upgrades are really needed at any given power/boost level, because requirements are different in street use and in racing conditions. The recommendations below are more street use orientated. In some cases I have put two options for same power upgrade. The "milder" one is for easy street use and the other one for e.g. some more serious racing/acceleration competitions.

The notes below refer to the upgrade numbers. Each upgrade will be briefly explained with information of possible sources and price levels. In many cases you find more detailed information of those in other parts of my web pages, in discussion forums or in suppliers' web pages. The prices are usually presented in Euros (€). Multiply euros by approx. 1.1 to get dollars. Note that price of same product may vary a lot from country to country due to manufacturer' different sales channels, different tax levels and volumes. Price references below are usually from European Union. USA seem to have the lowest price level on everything, even on the imported BMW parts.
I have excluded from the price ranges the very cheapest models, which I do think would not meet our quality requirements.

N= Not needed for this power level
R= Recommended for this power level
G= Good Idea
Y= YES, you should use it for this power level

Upgrade 1 2 3 4 5 6 7 8 9
Matrix of tuning options for BMW 745i (E23). Approximate price level 300 HP+
0,7 bar
10 PSI
350 HP
0,9 bar
13 PSI
400 HP
1,1 bar
16 PSI
450 HP
1,1 bar
16 PSI
475 HP
1,1 bar
16 PSI
515 HP
1,3 bar
19 PSI
580 HP
1,5 bar
22 PSI
635 HP
1,7 bar
25 PSI
700+ HP
1 Tuning Chip 205 Y Y Y Y Y Y Y Y Y
2 Wastegate Mod. 1 30-50 N Y Y Y Y Y N N N
3 Wastegate Mod. 2 200 $ N N N N N N Y Y Y
4 Cooler Spark Plugs 10 R Y Y Y Y Y Y Y Y
5 Turbo Gauge 30-250 R Y Y Y Y Y Y Y Y
6 Fuel Management Unit (FMU) 200-300 N R Y Y Y Y Y Y Y
7 Air/Fuel Mixture Monitor 100-300 N R R Y Y Y Y Y Y
8 HiFlo Air Filter 110 R R Y Y Y Y Y Y Y
9 2*2.5" Exhaust 400-700 N N N Y Y Y Y Y Y
10 Clean Intercooler Only work R


11 Copper Cylinder Head Gasket 195 N N/R N/R


12 Fuel Pressure Gauge 60-250 N R R/Y Y Y Y Y Y Y
13 Oil Temp Gauge 50-250 N R R/Y Y Y Y Y Y Y
14 Oil Pressure Gauge 60-250 N R R/Y Y Y Y Y Y Y
15 EGT Gauge 145-190 $ N G G G G G G G G
16 Steeper Camshaft 495 Y Y
17 Turbo Modification ??? N N N N N N


18 Forged Pistons and Rods See note N N N N R R R Y Y
19 Bigger Intercooler or water cooling N N N N/R R R Y Y Y
20 Larger pipes to/from Intercooler N N N N/R R R R/Y Y Y
21 Bigger Exhaust Manifold N N N N N N R R R/Y
22 "A-Pack" Upgrade N N N R R R Y Y Y
23. Higher Differential Ratio G G G G G G G G G
24. "Pure" Knock Signal to boost control line G G G G G G G G G
25. Additional Fuel Injectors in Intake Pipe N N N N N G G G G
26 Electronic Boost Controllers G G G G G G G G G
27. Good Life Insurance N R R Y Y Y Y Y Y

1. This is of course the tuning chip we make. Price 205 €. The only modification required for the lowest power levels of 300 HP+ is this chip. You then just have to either take off the control hose to the wastegate or put a simple valve in the hose to control the amount of air. With this basic modification alone your life will never be the same again. Not so much because of the power but because of the big increase in torque. Press the gas pedal half way down and wait your cheeks to press against the head rest. After that there's no return to factory set up. As simple as that.

2. Wastegate Mod. 1 is standard wastegate with additional boost control line to the upper chamber of the wastegate. This you can ask any metal shop to do. For further information of different ways to modify and control the wastegate please see the "Wastegate" section. Here you can see picture of  a modified wastegate, which has both the Mod. 1and the Mod. 2. installed.

3. Wastegate Mod. 2 is same as Mod. 1 but with a tension control on top. Available from 745Team at www.745i.com

4. Cooler Spark Plugs. Use one step cooler spark plugs than officially recommended.

5. Turbo Gauge. Use a gauge that shows also the vacuum; a good one is e.g. VDO CockPit International Series Gauge with -1 - +1.5 bar scale (or PSI scale) Price 60-70 . This is good enough for most power levels. In the very high end boost levels (over 2.0 bar or 29 PSI are possible) you need to use different turbo gauge. One of the best places to install this and the other add-on gauges is in front of gear shift lever, replacing the c-cassette holders.  We manufacture a special instrument cluster (Order ID: 3CL, Price 36 ), that fits exactly that space. You find further information in the "Products "section. See following pictures: Cluster+VDO kit, VDO Turbo gauge.
I will update the " Gauges " section in the near future with the VDO CockPit International Series information.

6. Fuel Management Unit (FMU) or as it is also called Rising Rate Fuel Pressure Regulator. This is needed to maintain sufficient fuel supply at higher boost levels. There are several different versions on the market. One of the best ones, which is succesfully used in many, many chip tuned 745i's, is Cartech model CAR-2022. Retail price is $259 in USA.
7. Air/Fuel Mixture Monitor. This is for your and the engine's safety. There are several different models in the market. One of the best (and in the higher side of the price range) is HALMETER AFR30 mixture monitor with a 3 or 4 wire O2 sensor. Available at www.halmeter.com

8. HiFlo Air Filter. A high air flow filter like K&N 33-2005  is always recommended when you increase the engine performance. Higher initial cost, but lasts 10 years and gives some extra horspowers (estimated min. 6 HP more in 745i) for almost nothing.

9. 2*2.5" Exhaust System. In theory 1*3" exhaust delivers more power, but 2*2.5" is more than sufficient in most power levels and a lot less noisy. Usually all 745i owners have had these made at their local exhaust pipe specialist. Shipping costs are too high from central warehouse to different parts of the world. Read more in the "Exhaust" section.
Note that the only difference between power level 3 (400 HP) and 4 (450 HP) is larger exhaust system. +50 HP difference seems to be on the lower side. 0.3 bar back boost in standard exhaust would mean more like 70 HP difference.

10. Clean intercooler. All 745is are 17-25 years old. I bet that in many of those the intercooler has never been cleaned. If you have not done it, do it now and feel the difference (more power!). This is also a must when you change to a Hi Flo Air Filter. Take off the intercooler. Flush it thorougly with gasoline. Then wash it with water and dry it with compressed air. Make sure that there is no gasoline inside when you reinstall it.

11. Copper Cylinder Head Gasket. We have supplied a lot of tuning chips for the 745i owners all over the world and as the users have gradually increased the power levels of their engines the only problem has been blown gasket; sooner or later. Not everybody have had that problem even at very high power levels, but realistically the gasket is "the weakest link".
That is natural and fully according to the laws of physics. The standard gasket can only withstand certain amount of pressure. Copper gaskets are typically used in racing cars due to reliability and as those can be used several times.
Whenever engine power exceeds 100 HP/L a copper gasket is highly recommended. In case of BMW 745i engine that limit would be 340 HP.
This is a bit grey area when you should change over to copper gasket. It really depends a lot of driving habits and purpose. If you just use your car for daily drive with occasional power bursts the standard gasket could last very long time even at 400+ HP levels. If you like to participate sunday club races you should change to copper gasket already below 400 HP. Anyway I recommend that whenever you need to open the head change to copper gasket at the same time. It does not cost too much more than standard gasket. We recommend 2.00 mm gasket for 745i, but other thicknesses are available also. The standard 745 gasket thickness is 1.72 mm, but when the head is fully torqued it goes down to approx. 1.5 mm. With 2.0 mm copper gasket you lose a bit in non-turbo power, but gain a lot in turbo power. Also, if you have your head/block milled then the 2.00 mm gasket will compensate for it. Copper gasket is available e.g. at SCE Gaskets, http://www.scegasketsonline.com/ . The best thickness is 0.080", order code 91028. The other possibility is http://www.flatoutgroup.com/gaskets/am.asp . Here's what they say on their site: Flatout has developed an "out-of-the-box" copper head gasket that requires no addition preparation before installation. Head gaskets made with Rubber Coated Copper, RCC, assemble directly from the package, seal fluids and combustion better than any other copper gaskets, and remove effortlessly with no messy clean up. The rubber coating used for Rubber Coated Copper gaskets is inert to almost all fluids and solvents and can withstand the extreme temperatures produced by the hottest drag motors. This dry coating is very thin to ensure low torque loss and is durable enough to be reused in most cases. Again, the best thickness is 0.080". Their price level is about $225.

12. Fuel Pressure Gauge.  This gauge is recommended especially with the FMU. It gives you security and "peace of mind" that mixture will not go lean because of problems in fuel supply line. If there is a problem with fuel pumps, leaks or fuel filter you will see it immediately. You can also follow how the fuel pressure increases with boost. Sofar I have not found a "real" fuel pressure gauge, so at least most of us are using oil pressure gauges for this purpose also. In the VDO CockPit International Series you can select between 5 bar and 10 bar scales (or USA versions). Price level including electronic sensor 80- 90 . Actually the sensor costs more than the gauge. Cluster+VDO kit, VDO Pressure Gauge

13. Oil Temperature Gauge.  Good to have but not absolutely necessary. If you stick with the 4 gauge cluster you may want to change this to the EGT Gauge. VDO CockPit International Series  Oil Temp Gauge has 0- +150 C scale (or USA version). Price level with electronic sensor 65-75 . VDO Oil Temp Gauge

14. Oil Pressure Gauge. This is the most important gauge in any high performance / racing car. Dropping oil pressure means immediate serious trouble. In the  VDO CockPit International series  this is the same as the above Fuel Pressure Gauge.

15. EGT (Exhaust Gas Temperature) Gauge.  EGT manufacturers and Fuel/Air Mixture Monitor manufacturers are kind of rivals. Both claim that their products should be used to monitor mixture and to detect lean/rich situations. I guess both have a good point. I have not yet used this gauge so I will not second guess which one is better. First I had some difficulties to find EGT gauges (at least in Finland) suitable for the 745i, but then found a lot in the web. VDO has one also in their CockPit Black Series, which is close enough to use with the International series in the same cluster. Price in USA is 145 $ - 190 $.

16. Steeper Camshaft. The only difference between power levels 4 (450 HP) and 5 (475 HP) is a Schrick 284 steeper camshaft. We do not recommend over 290 due to unstable idle. The estimated power increase is min. 25 HP due to a shift of max. power RPM point a bit further up. Torque in low RPMs will be a bit less, but who really cares because it is so high anyway. As you can see I have put steeper camshaft into the matrix only into two power columns as an example. You can add it yourself to any other column to see the impact on power and price at your selected upgrade level. Here's a picture of the Schrick tuning camshaft.
Some 745i owners have installed even steeper camshafts. For instance one has 300. Owners comment: "At idle the rpm is at 900RPM but you always feel the engine shivering and unbalanced, but once you push the pedal every thing is O.K."

17. Turbo Modification. I have been informed of many different kind of turbo modifications that have been made to the KKK K-27 turbo in order to increase power. The approaches have been different depending on local turbo shops preferences, skills and knowledgement of the KKK turbos or on owners requirements. In one example the number of blades was increased from 12 to 16. The result was that the turbo needs more engine revs to start charging, but produces considerably more boost in the top rev range. The owner compensated that by changing the differential to >3.5 ratio.
In another example the blade angle was modified. I don't know yet how, but the owner claims that the turbo lag is reduced and that it provides more power. I am expecting to get more information of that modification.

18. Forged Pistons and Connecting Rods and special Racing Rings for stock pistons.  In this category you can increase power and reliability in three different ways; using any or all of them. There are also three main reasons why forged materials are used in Racing and High Performance engines:
1. Reliability and ability to withstand higher temperatures (also better heat transfer) and forces without meltdown or deforming.
2. Forged pistons and connecting rods weight less. That equals to more horsepower, because these are fast moving parts. The more these weight the more mass has to be moved = more energy is lost.
3. Less friction = more horsepower. Modern forged pistons are usually also coated with special materials to reduce friction and to increase lubrication.

If you ask these manufacturers when these kind of products should be used in your engine a typical answer is "always when power is increase by 50 HP over stock and definitively when power is increased by 100 HP or more over stock." Now, in our case we all should be using these if we follow these instructions literally. Of course they want to sell their products as much as possible, but I think that we can be a lot more conservative. The M106 engine is very rugged design and can withstand much more than the factory 252 HP without any problems. Of course I would like to have always the best pistons/rods, etc..., but it is also a question of money.

The three different ways to increase power:

1. Performance Rings for Stock Pistons
This is the easiest and most economical way to get some of the increased reliability and increased power of the forged pistons and rods. These are usually similar ring sets to those used with forged pistons, but designed for the standard pistons. Only a fraction of the cost of full forged piston/rod kit and these actually work.
Typical example is TOGA Performance Plasma Moly Rings. Ring set for BMW 745i, order no: PMBMW-102 (M106 only), costs $119 in USA at www.importperformanceparts.net, they are part of Flatlander racing.  Ask your local BMW tuning specialist for these or equivalent parts.

2. Forged Pistons
We 745i owners are in good position in the respect that there are many piston manufacturers both in Europe and in USA who manufacture forged pistons for our engines. Note that sometimes they just list pistons for BMW engine type "M30B35", but when asked they either know the M106 or say that they can supply to any compression ratio customer wants. For instance Phil Carlino from Flatlander Racing  (USA) answered to me " I can supply any piston in size or compression $140 each with pins". Usually these pistons are supplied with same quality pins and rings as the pistons are.
Mahle is one of the leading European manufacturers of pistons and connecting rods. Their products are also used in the F1 cars. They only sell the racing products through specialist tuning companies in each country. So you need to find those companies.
Other companies that make forged pistons for 745's are e.g.:
Venolia Pistons are available worldwide. E.g. at Import Performance Parts (USA) the 745i pistons cost $98 each plus rings and pins. In Sweden Venolia pistons are available at Powerparts Ab. Just to give you a couple of examples.
JE Pistons  is another source for 745i forged pistons. Available e.g. at Import Performance Parts.Price about $100 each plus something for rings.
These were just some examples of known piston suppliers for BMW's. If you know of any other manufacturer please send to me jarmo.havulinna@viinikellari.com a note and I add it to the list.

3. Forged Connecting Rods
As I said many of the piston manufacturers make also connecting rods. There are however a number of specialist companies concentrating on connecting rods. Companies like Manley, Probe, Lunati and Pauter, who manufacture really top-of-the-line racing rods also for the BMW big 6 M30/M106 engines. These rods are 250 gr lighter than standard. The price at Import Performance Parts is about $980 for a kit of 6.

19. Bigger intercooler (IC) or water cooling. The purpose of an intercooler is to reduce intake air temperature as much as possible. The compressed air coming from the turbo is hot and the temperature is also  directly relative to ambient temperature. This is not so much an issue in Northern countries than it is in south, obviously. The standard 745i intercooler is good and can be used up to very high power levels, eventhough the efficiency goes down at certain point. So you lose some of the power you would otherwise have with better air cooling system.
I once installed temp. sensors before and after intercooler to monitor performance versus temperature and temp. drop over IC. I could feel that whenever temp. after intercooler rose to 55 C the power started to go down. So this was just based on feeling, not real calculations.  If you want to know more about theories and calculations visit e.g. Ray Hall Turbocharging web site in Australia. They have a lot of good technical information and calculation softwares covering e.g. Intercoolers and "Water to Air Intercoolers".
One idea is water injection, which is used in WRC cars for cooling and increasing oxygen content in intake air.
Here is one real example of 745 intercooler upgrade:
One owner designed an intercooler, which extented upwards close to hood. Width was unchanged. As a result cooling area was considerably increased and all of it well exposed to outside air. The problem was that there was no more place for the standard air filter and air intake in front of the car. He had to use custom designed K&N filter just after the AFM. See the picture. In my opinion this solution has two disadvantages which more or less offset the advantage of this kind of larger IC:
1. Having the air filter inside the hood over the engine means a lot higher intake air temperature than in OEM solution.
2. There is no direct "air path" from outside to the air filter.
I personally think that this kind of solution does not give much, if any benefit over standard solution.

I have seen that this is quite popular topic in many discussion forums and many good ideas have been analyzed. Please send me suggestions and real examples and I will add those here.

20. Larger Pipes to/from Intercooler. Brian Nawrocki  (USA) <brian.nawrocki@saint-gobain.com> has designed a nice set of intercooler pipes for the 745i. Here's his description of the products:
"The pipes are bent from 304 series stailess and are CNC bent. They fit perfectly. The guy who bends them for me has a machine that takes a 3-D profile of the original pipes and then bends the new stainless on the axis of the originals. The lower pipe (turbo to inter cooler, IC) is 2" and the upper pipe (IC to Alum. intake pipe) is 2.5" with the ends swaged down to 60 mm to accept silicone turbo couplings."
Please contact Brian directly for purchase/more information. I can supply these also for international customers in a "package deal".

21. Bigger Exhaust Manifold. This seems to be a good idea in the very high power levels. Recently I received an email from one 745 owner who said that they are working on such design. He promised to keep me informed of the progress. I will keep you posted in here. Of course you can get similar power out also from standard exhaust manifold, but with higher losses due to resistance.

22. "A-Pack" Upgrade of the Transmission. Almost always when 745 tranny fails the problem is worn out "A-Pack"inside the transmission. You can buy a "stronger than original" repair kit for this.  I have the details somewhere, but not at hand while I write this summary. Could someone, who has done this upgrade recently send me some details of it so that I can add the info here?

23. Higher Differential Ratio.  This upgrade has nothing to do with increasing the HP but everything with increasing the torque. Torque increases between tyres and road surface in direct relationship to overall rev ratio between engine and tyres ( See the HP vs. Torque section for details). So by using higher diff ratio you increase
the torque, which in turn gives you faster acceleration. This is an easy and simple way for any E23 owner to increase acceleration. When you win something you usually lose something. In this case you lose on top speed and on fuel economy.
The standard final drive in 745's is either 2.93 or 3.07:1. With 2.93 ratio first gear alone takes you to about 100 km/h, so there is a lot of room to play with. Some have changed to 3.25/3.45. Others swear by 3.64/3.73. Some have switched to as high as 3.91.
I would appreciate receiving information on exact Getrag types used in these conversions ( I've seen mentioned e.g. model 265, etc.., but I personally don't have any experience on these. I still use 2.93, because I love the +330 km/h top speed possibility ). I will add such info here so that other users can benefit of it, too.
Thanks to Rick for suggesting this subject and giving me the above info.

24. "Pure" Knock Signal to Boost Control Line.  By having a pure control line directly from the knock sensors you can lower the engine power at any high boost level immediately when knock occurs. The same line can also be used for knock indicator lamp or LED. This is something you need to make and as far as I know nobody has done it yet. You will find instructions in the "Knock Box" section in this web site.

25. Additional Fuel Injectors in Intake Pipe. Juha Tuoma, who is one of the pioneers in 745i tuning, used this approach in his car in the late 90's instead of a FMU. So this is a useful alternative to FMU, but much more expensive. In very high power levels you could use both solutions. Two fuel injectors are added to the intake pipe. These are controlled by a separate computer, which can be programmed to turn the injectors on at any boost level. Juha used approx.1.0 bar threshol, if I remember right. You can see the set up in this picture.

26. Electronic Boost Controllers. Many of you have asked for this. I have tried to find suitable electronic boost controllers for 745's, but sofar I have not succeeded. There are many different versions available, but none to my understanding such, that can easily control both upper and lower chambers of the wastegate. I may be wrong. You can check yourself from the list below. The best solution may be to buy two valves with stepping motor control. That way both upper and lower chamber pressures could be easily controlled from the cockpit with two potentiometers.
Here is the list of electronic boost controller manufacturers that I have found:
Trust/Greddy - Profec E-01 (Solenoid Valve), Profec (Stepping motor), Profec B Spec (Dual solenoid valve)
Blitz - DUALSBC Spec R (Dual solenoid valve), DUALSBC Spec S (Solenoid valve), SBC-iD II (Dual solenoid valve)
HKS - EVC (Stepping motor), EVC EZ II (Stepping motor), EVC IV (Stepping motor), EVC Pro (Stepping motor)
A'PEXi - AVC-R (Solenoid valve)
GRID - DBC Type-2001 (Solenoid valve), DBC Type-M (Solenoid valve), Synchro DBC (Solenoid valve *2)
Here is a Guide to boost controllers.

I have received many inquiries about supplying different kind of tuning packages based on the matrix. Especially from countires/areas where it is difficult or impossible to buy these locally or through Internet. Unfortunately I can not do it. I tried it, but the work load involved was too just too big without additional workforce, which is not possible in this kind of "hobby".

I would appreciate very much your comments, suggestions and corrections to this guide. A lot of it is already now based on users' experiences.