How to read a turbo map

To really get the cooling properties of alcohol, you'll need aux injectors after the compressor exit, you want to cool the charge before it enters the combustion chamber.  There isn't much time for the E85 to cool the charge where the port injectors place the fuel right behind the intake valves.  E85 definitely has other benefits than cooler charge temps, the main power benefits are "no" knock which lets you run closer to MBT, the cooling effect is helpful but not nearly as significant as this.

Be cautious with E85, it does not "knock" in the traditional sense, most knock sensors are deaf to it.  It burns much quicker than gasoline, which leaves less time for knock to occur during combustion. Which is great for making power, you can run less timing to make the same power as gas! But you can easily run too much timing (past MBT, over advanced, not good), or run timing too close to MBT at high RPM/load and get massive cylinder pressures which can quickly lead to hardware failures.  Getting a proper tune by an experienced tuner is critical when you're running that much power on E85 (or not), the risk for failure is quite high.

Most tuners would mostly ignore the knock sensor on E85, and use a chassis dyno to tune timing (find MBT and back off a bit for safety factor), being mindful of the hardware limits of the engine.

Good info here, HPA is a good resource for tuning.

https://www.hpacademy.com/courses/ethanol-and-flex-fuel-tuning/

https://www.youtube.com/watch?v=m-Sj8WkWH6E

https://www.youtube.com/watch?v=RTzW4V3t7JY

Two comments on the above:

1) additional non-port injectors are a band-aid at best, and can have fuel flow distribution issues that can go wrong quickly. From the testing I have done having injectors far up in the runners have the same, if not more, benefit without this issue. More hardware and double the injectors, plus need to control them. Most of the vaporization necessary happens when the valve opens. Usually not worth it to fool with anything but one injector per port, properly sized.

2) E85 can definitely knock depending on compression ratio, cam choice and chamber design, it's just much harder for it to happen. Generally the timing required for knock is so far past MBT that you don't get into it if you know what you are doing, even a little. Also, it doesn't burn quicker (most tests are at stoich) and with richer afr it can burn much slower than gasoline (as evidenced by more timing for MBT). 

This all being said, give the motor what it likes, that's always the right answer.

Paul_VR6 (Forum Supporter) said:

Two comments on the above:

1) additional non-port injectors are a band-aid at best, and can have fuel flow distribution issues that can go wrong quickly. From the testing I have done having injectors far up in the runners have the same, if not more, benefit without this issue. More hardware and double the injectors, plus need to control them. Most of the vaporization necessary happens when the valve opens. Usually not worth it to fool with anything but one injector per port, properly sized.

2) E85 can definitely knock depending on compression ratio, cam choice and chamber design, it's just much harder for it to happen. Generally the timing required for knock is so far past MBT that you don't get into it if you know what you are doing, even a little. Also, it doesn't burn quicker (most tests are at stoich) and with richer afr it can burn much slower than gasoline (as evidenced by more timing for MBT). 

This all being said, give the motor what it likes, that's always the right answer.

Good points.

I have to disagree with part of point #2, it has been proven empirically that it does have a faster flame front propagation speed than gasoline, at all air fuel ratios.  That's one of the reasons why it makes more power (IMEP) than gasoline at the same ignition timing. The difference does change with lambda, but you'd have to be running extremely rich (lambda <.7, eq ratio >1.4) for them to have similar flame front speed.

Now when you're talking about pump E85 in the real world, I can see that there isn't much difference.  Most "E85" at the pump varies so much in ethanol content, you're lucky to ever get true 85% ethanol, and that would only be during summer months in most states.

https://hal.archives-ouvertes.fr/hal-00853563/document

https://www.sciencedirect.com/topics/chemistry/flame-speed

Paul_VR6 (Forum Supporter) said:

Two comments on the above:

1) additional non-port injectors are a band-aid at best, and can have fuel flow distribution issues that can go wrong quickly. From the testing I have done having injectors far up in the runners have the same, if not more, benefit without this issue. More hardware and double the injectors, plus need to control them. Most of the vaporization necessary happens when the valve opens. Usually not worth it to fool with anything but one injector per port, properly sized.

2) E85 can definitely knock depending on compression ratio, cam choice and chamber design, it's just much harder for it to happen. Generally the timing required for knock is so far past MBT that you don't get into it if you know what you are doing, even a little. Also, it doesn't burn quicker (most tests are at stoich) and with richer afr it can burn much slower than gasoline (as evidenced by more timing for MBT). 

This all being said, give the motor what it likes, that's always the right answer.

Do you have any data from your tests you can share? Sounds like a fun study on injector placement. Agreed it gets too complicated with multiple injectors.

Paul_VR6 (Forum Supporter) said:

Two comments on the above:

1) additional non-port injectors are a band-aid at best, and can have fuel flow distribution issues that can go wrong quickly. From the testing I have done having injectors far up in the runners have the same, if not more, benefit without this issue. More hardware and double the injectors, plus need to control them. Most of the vaporization necessary happens when the valve opens. Usually not worth it to fool with anything but one injector per port, properly sized.

 

I'm pretty sure I can talk about it now 10 years later, but I did software for the Corvette ALMS team. They ran a set of DI injectors in the runners as well as in the cylinders with mapping to blend the two however they wanted. Even with the restrictor and no boost, they found some decent gains with the system. I do agree with you that additional injectors should never be added just to get more fuel - that should be done with the correct injector where it is  supposed to be - but their experiment did prove that some balance was beneficial when running DI port injectors and alcohol fuel. Indy at the time also ran a similar dual setup for the same reasons, but I didn't work on that directly. Pretty sure those guys knew a thing or two about what they were doing though 

I will have to see what is still under NDA and what isn't and see what I can share. All of the injector stuff got paid for by others  which locks up the data in a few ways. 

On the flame speed front I have the following numbers in my notes, no clue where they are from at this point as they are 20+ years old likely out of an old crusty book:

Gas .34ms

Ethanol .39ms

Methanol .43ms

All at stoichiometric from what I remember, likely in open air, and that obviously can change in an engine.  There is also a difference between the front speed and how they build pressure, and how quickly they build to peak pressure. I can't see how ethanol has a faster burn rate/flame speed but then need more ignition lead. It's counter intuitive, and doesn't line up with my experience.

Edit - it's likely the @ AFR being the difference, that chart above is in equivalence ratio (1/lambda) so for most high power ethanol cars it would be all the way to the right (~1.33) and for methanol it would be off the chart to the right (~1.6). Just looking at the trends on that end of the chart, the order of results would change a bit.

Paul_VR6 (Forum Supporter) said:

 

Edit - it's likely the @ AFR being the difference, that chart above is in equivalence ratio (1/lambda) so for most high power ethanol cars it would be all the way to the right (~1.33) and for methanol it would be off the chart to the right (~1.6). Just looking at the trends on that end of the chart, the order of results would change a bit.

Yep, I think that's the difference! We're talking about the same thing, it's just relative to AFR (Iambda or eq ratio is better since that takes stoich differences into account of course!).  Lab and simulation conditions rarely match the real world, so I agree do what the motor likes and what feels right with your judgement. Ideally doing that port injection study on an engine dyno, with combustion pressure sensors, then you can really characterize the differences.  It's probably already been done, just a matter of finding the published SAE paper or journal. It's all interesting stuff, we need to have a GRM combustion seminar!

I think the other discrepancy with race ethanol fuels is they are more controlled, the latest indycars run E98 which is basically E100. The charge cooling benefits of aux injectors upstream are probably much more worth the complexity than if you were to use pump E85 (summer "1" class E85 is a minimum of 79% ethanol, class 2 blend is 74% ethanol, winter class 3 blend is only 70% ethanol). 

And they're looking for every 1/10% HP within the ruleset, Frenchy probably will be just fine with a V8 Twin Turbo on pump gas, let alone E85 with aux injectors!  Keep it simple, you can always go to E85 later!  I'm always shocked by the lengths people go through to run "E30" or other tunes, without a flex fuel sensor it's risky business.

In reply to engiekev :

There has to be some cooling benefit in a turbo engine to E85 allowing for power increases, not just the octane or faster burn.  I saw a highly turbocharged engine (call it a 10:1 compression 4.5l, inline valve pushrod V6) pick up about 12% by switching from C16 race fuel to E85.  So, it was not octane limited. (about 850hp to about 950-1000, depending on your math)

The interesting thing is, the same person (a well regarded tuner, not me  ) tuned it for both fuels, and the ignition mapping was nearly identical.  So either it was retarded for C16, advanced for E85, or at the chamber pressures seen, the difficulty in lighting off the wet fog compensated for the faster burn.

Pete. (l33t FS) said:

In reply to engiekev :

There has to be some cooling benefit in a turbo engine to E85.  I saw a highly turbocharged engine (call it a 10:1 compression 4.5l, inline valve pushrod V6) pick up about 12% by switching from C16 race fuel to E85.  So, it was not octane limited.

 

The interesting thing is, the same person (a well regarded tuner, not me  ) tuned it for both fuels, and the ignition mapping was nearly identical.  So either it was retarded for C16, advanced for E85, or at the chamber pressures seen, the difficulty in lighting off the wet fog compensated for the faster burn.

C16 is not oxygentated, E85 is

Pete. (l33t FS) said:

In reply to engiekev :

There has to be some cooling benefit in a turbo engine to E85 allowing for power increases, not just the octane or faster burn.  I saw a highly turbocharged engine (call it a 10:1 compression 4.5l, inline valve pushrod V6) pick up about 12% by switching from C16 race fuel to E85.  So, it was not octane limited. (about 850hp to about 950-1000, depending on your math)

 

The interesting thing is, the same person (a well regarded tuner, not me  ) tuned it for both fuels, and the ignition mapping was nearly identical.  So either it was retarded for C16, advanced for E85, or at the chamber pressures seen, the difficulty in lighting off the wet fog compensated for the faster burn.

There is a benefit, just not as much as the gains from being able to advance timing.  I lost the link but will try to find it.  Something like 10-15% gain in torque from timing advance, and only 3-4% benefit from the evaporative cooling effects with E85.

This topic is a rabbit hole and quickly you'll be reading thermodynamics textbooks and combustion books like Taylor and Heywood before you know it.

Different link, but still interesting:

2010 Study by MIT on a GM Turbo Direct Injection E85 vs Gas:

https://dspace.mit.edu/bitstream/handle/1721.1/59952/676953430-MIT.pdf

"Gasoline was also much more sensitive to intake air temperature changes than E85. Increasing the intake air temperature for gasoline decreased the peak pressure, however, knock onset began earlier for the higher temperatures, indicating that end-gas autoignition is more dependent on temperature than pressure. E85's peak pressure sensitivity to spark timing was found to be about 50% lower than that of gasoline and it displayed much higher knock resistance, not knocking until the intake air temperature was 130*C with spark timing of 30' bTDC."

E85 didn't knock until 266 F intake air temperature, that is very high.  They ran a "spark sweep" on the dyno (RPM constant, load constant, spark changing only) at these IAT temperature points. Notice they couldnt even run test with gas beyond 40*C intake air temperature, it would just knock.

"As is evident from the data the E85 generally gives about 2.5% higher NIMEP at 20'C IAT in the small spark regime gasoline could tolerate. It also features much more tolerance to spark advance, as up to 300 bTDC of spark advance did not induce knock until the maximum IAT of 130'C was reached."

Point is, you can run way more timing up to TDC with E85, and at higher intake air temperature limits before knock. And at the exact same conditions, E85 will produce 2.5% more torque (based on this data). 

Good call on the intake temp, I usually pull 1deg per 10deg IAT on gas and literally nothing until 150F on E85/E98.

Thanks for clarifying the other points you made, appreciate the discussion.

I just noticed on this chart you can see where they go past MBT with the E85 fuel (MBT circled for the 20C E85 data points).  This illustrates my point about how one could easily just keep adding numbers in the timing table on their tune with E85 and never knock, then start making less power because they are over advanced.

In reply to 03Panther :

My Jaguar XJS V12. That I wanted to save and sell to a restorer. But the more I thought about that plan the more I decided to heck with it.  
      Looking for what I can expect for 1/4 time. I found  in 1982 someone with a XJS V12 did a 9.710 @137 mph in the 1/4 mile. So there's my target 

In reply to engiekev :

The 40C figure is interesting to me, only because that coincides with what a regarded turbo rotary tuner said about 15-20 years ago: the most critical thing was keeping intake air temps below 40C.  After that, you'd run X timing (based on engine port - lower VE ports needed more timing, natch) and no leaner than Y lambda, and you'd be good to go.

Regarding the single point of data I brought up, I wonder how much of an effect the engine's aluminum engine and block had.  Sucks the heat right out of the combustion, so maybe a cooler burn means less heat lost to the engine in the first place?

Just trying to noodle out how a switch to a lower octane fuel allowed much higher power levels.  The guy who tuned it said, basically, you could run the engine so lean/advanced that you'd pour the pistons out of the sump plug before you got it to detonate on C16, so I don't think it was an inability to get to BMEP.

It all makes me somewhat regret the 7:1 pistons in my turbo Audi engine.  The idea was pump gas with water injection at high boost, now I'm wishing it had 9:1 and E85.

In reply to Pete. (l33t FS) :

Same here. Stock pistons are either 7.8-1 or 11.5-1 the European ones are 9.0-1 &12.5-1 but they get silly money for those. 

In reply to frenchyd :

These were custom .5mm overbore forgings, that had the dish milled out "considerably".  4 of the 5 were in a 2 liter "bubble block" that made 300hp on CIS injection and pump gas, this engine is essentially just 25% more of everything.  Expensive pistons plus machine work.

At least it's a proven combo.  And I should be able to make more than 25% more power with EFI and coil on plug ignition rather than CIS (an instant 10% power hit due to the spill plate's restriction) and a mechanical distributor.

Just run your 7:1 pistons on E85 and crank it. Will feel a little lazy compared to a high compression setup, but it will fly once air starts moving.

Paul_VR6 (Forum Supporter) said:

Just run your 7:1 pistons on E85 and crank it. Will feel a little lazy compared to a high compression setup, but it will fly once air starts moving.

Agreed 7:1 is probably fine with forced induction, it will just be lazier before you get the turbo spooled up. Maybe you can play with timing and fuel to get some more exhaust energy into the turbine at low RPM, pseudo anti-lag.

I think your's is a good example of why you need to have a set definition of fuel type before a build is started, it really does dictate a lot of engine parameters (compression ratio, target peak power RPM due to less or more knock limited range, fuel system components, forced induction components).  On gas 11:1 is likely too high a compression ratio, on E85 it could work just fine even with boost.  

Looking at other examples, these guys suggest a CR of 15:1 naturally aspirated E85 would not be unrealistic.

https://www.onallcylinders.com/2015/11/20/ask-away-with-jeff-smith-what-is-safe-effective-compression-ratio-for-e85/

Quite a different realm, but IndyCar was mentioned before. They run 11.5-12.5:1 (allegedly) with high boost on E85 (I thought they used E100 before, I was wrong):

https://dsportmag.com/the-tech/education/performance-tech-compression-ratio-101-part2/

In reply to engiekev :

Pretty sure it's E98. E100 would have the booze tax on it. 

MrJoshua said:

It looks like it might be possible to flip the exhaust manifolds left to right on the V12 Jag and run them facing up. That puts the turbos up high and easier to fabricate an adapter for. They might foul the factory fuel injected motor intake though. 

 

Edit: if you are running non intercooled it might let you just run a small intake pipe straight from the turbo outlet to the throttle body.

Sorry I missed your post earlier. No you can't flip the manifolds upside down.  The outlet is very close to the block  and reversing them would have that hitting the head before you can bolt it down. 
what I did when I kludged a pair of T2 Saab turbo's was use a u-bend pipe to get the turbo outlet in line with the FI inlet. I did have to clock both of them to get everything lined up. But it was sturdy and if I worried I could have built a bracket to go to the inner fender. 

Paul_VR6 (Forum Supporter) said:

Just run your 7:1 pistons on E85 and crank it. Will feel a little lazy compared to a high compression setup, but it will fly once air starts moving.

That's what I plan on doing. Road racing is all above 3500 rpm  and redline is 6500. Very conservative with the short (2.75 stroke) plus the factory ran the engine at 8300 before any valve bounce occurred.  Since it uses the same valve springs the Cosworth formula 1 engine used  I'm very comfortable with taking it up to 7000 rpm. 

frenchyd said:

In reply to engiekev :

Pretty sure it's E98. E100 would have the booze tax on it. 

Yep, they usually add 2% methanol to keep it from being sold as fancy moonshine.

Please post pics of this glorious engine build soon!

In reply to engiekev :

OK here a start. 

Look Ma, no combustion chamber. A real Flathead!  
Actually those are just stand ins. I might not have to rebuild it.   Just grab one from my pile and toss a pair of turbo's at it. 

frenchyd said:

In reply to engiekev :

Pretty sure it's E98. E100 would have the booze tax on it. 

Where do you get your facts?  One it's E98 because it's impossible to distill pure ethanol.  I do question the E98 because the limit is 95.6%.  Ethanol fuel does not have a "booze tax" on it because it's produced under special permit for use only as a fuel.