Question: Can we put an 8-71 blower on a high output, normally aspirated Big Block V-8 with very high compression ratio (15 to 1)?
Answer: The detonation can be controlled with enrichment and air to fuel ratio control, theoretically regardless of the compression ratio. However, I am not sure about the mechanical strength of the components.? With that real high compression using a blower and a wedge head, the power stroke starts on one side of the dome. If you are using short skirt pistons or pistons that are not full circumference at or below the wrist pin (typical of normally aspirated high output engines), you may have a problem with skirt deflection, breaking a piston, or galling it. An 8-71 Roots blower, at 10% overdrive, theoretically pumps the same amount of air as an engine approaching 900 cubic inches. The math for that is in Fuel Injection Racing Secrets. Stuffing that amount of air into your BB engine gets a lot of boost and loading. FYI; Our book 5000 Horsepower on Methanol provides information about actual compression ratio with supercharging including simple math on how to determine it.

Question: How did you dial in your mechanical fuel injection setup for bracket racing?
Answer: Our tune-up is set up to be in a linear range. That is when we increase the shift point, our ET is proportionately lower. When we lower our shift point, our ET is proportionately higher.? That is a result of many characteristics from our combination, some intentional and some accidental.

I recall a setup many years ago that was not linear. If you raised the shift point beyond a certain point, you slowed down. The cylinder heads were small and acted as the limiting factor in the combination.

The subject of linear is an extensive one. Keeping everything moderate is a good step in that direction: moderate timing, launch point, shift point, and fuel enrichment. In our case, we know what our air to fuel ratio is from jet area and air calculations from Fuel Injection Racing Secrets. We know our rich air to fuel ratio limit and our lean air to fuel ratio limit and we keep in the middle. It is difficult to get there without record keeping and some calculations or data measurements. And we found that method to be very repeatable year after year after year. And once we found it, we race in that range and never had to recalculate or find it again.

In addition to the math in the FI book, a lot of text and editorial are provided about fuel injection. However, the correspondence that follows is from a ‘Fuel Injection Book’ customer. It is a demonstration of the extent that a tuner can get into from the FI book math section. (more…)

Below is an email correspondence I had with Jimmy:

Hi Bob, I talked to you last week through email about doing a MFI Enderle Birdcatcher on gas on the street … I will use your book to set up and tune my system. But i have a question that may not be covered in your book. I hate the way the air filters look for the hats, it hides the butterflies and i want mine to be seen. I talked to a guy that designed an inside air filter and he said it worked good for short while until the cotton between the wire mesh got soaked with fuel then it cut air flow way down. He said even though the blower is sucking air and fuel down you still get fuel bouncing around in the hat. My question is this: they sell all steel air filters for cars now, what if I designed an all steel (stainless) air filter to be mounted right behind the butterflies would you think that might work? That way if fuel did get on it the air flow would keep it blown through. This is a prostreet car I will drive only about twice a month to the local car shows we are talking about only driving in pretty weather and I would take the filter out for the race track. I was just trying to figure a way to run a filter on it without running one of those front mount filters. I also see people running those BDS efi bugcatchers with no air filters, there is a guy running a blown coupe like that and he said he is not worried about running with no air filter no more than he drives it. I’m running a blown BBC with a Littlefied 871, the blower is set up for gas on the street with no teflon strips so its not real tight. I just don’t want to score the inside of my blower and cylinders all up. No more than I drive it on the street it may not be a big concern. Thanks for any advice you can spare…J

(more…)

Message: in your book you show a vacuum gauge with a telltale, do you know where to obtain one of these gauges?? KS

It is not a vacuum gage but a pressure gage. You probably want a 0-200 psi, liquid filled, tattle tale gage. I was told McMaster has them. McMaster is a large gage supplier. I did a web search awhile back and was able to locate them. I do not have any further info from that.

In addition, locate the gage connection after the barrel valve to get the injector pressure after the bypasses and the pump relief pressure. You can tie into any extra port in the distribution block or tap into the block if no added ports are available. Many do not firmly connect the gage to the engine. It is left hanging loose so that engine vibrations will not destroy it.

Good evening Bob,
Thank you for both your reply and the Book, it arrived yesterday and from that moment till this morning other than doing the everyday thing I can not put the book down without reading the next and then the next page!! It is a work of art and will be enjoyed for a long time.? I read of your experience at the start line (from Bob’s IHRA free article downloads) and understand the importance; in my case both as a driver and a president of the track I agree that the starter has the ROLE and was acknowledged accordingly… DM

Thank you, DM, for your feedback. I agree that the starter is important at the track. I’m glad you found the IHRA articles helpful.

I read your book but I had a question regarding the pre-run cylinder head temps and oil temps. I have an aluminum rod 400CI SBC turbo car with no coolant in the block. I’m measuring cylinder head temperature and oil temperature and wondering what’s a safe range to be in?
Depends on whether you are running gas or alky. With gas and real high boost and limited cooling in the engine, you may need to be real cool at the start. With methanol, you can heat or cool the engine at idle with enrichment and heat or cool after the start of the run with enrichment. In the later case, you should decide whether you want to launch your race vehicle at some oil temp over the boiling point of methanol, to boil away the methanol, or higher for more fuel vaporization. The highest I have heard that is run successfully is about 210 deg F. and sustained on the run. With no water in the block, you are susceptible to hot spots that may cause cracking, regardless of the temp you are starting with. One combo that is common is to start at around 160 to 180 and keep it there through enrichment on the run. You also have to look at the rate of idle temp rise before the run. A high rate of rise to get up to 160 before the run may be too high in that it may continue to rise fast in the event of a delay at the start. In that case if you are up over 220 or 240 after a start delay, that may be too much heat. In that case getting more idle enrichment to delay the engine heat build up would be better. Although the engine may be cool for a normal start when the delay does not occur. If you have a heat gun, check heads and block at various locations and times to develop a learning tree. The engine will tell you when it is too hot. You will see other events occurring like an overheated plug or smoke coming from the engine or bearing wear from oil break down.
At what temperature is overheating? Thanks, PT
I have heard that over 220 deg F is a bit high for a small block. Again with a dry block and high boost, hot spots can develop at lower starting temps. There are no standards. Just try it and keep an eye on cooling passage sealing. You may want to close off the cooling side of the block and pressure test it to see if it holds pressure. Then check that from time to time. If it will not hold pressure due to cracking, that is the start of a failure no matter how small the cracks.
We have run some hemi stuff with cast iron cracks and they lasted OK for a while. You just never know.
FYI: You want the oil over the boiling point of methanol to boil the methanol away. If it is gas, it does not separate from the oil, so that is not the limit. Probably not over 220 for lube failure avoidance. You want the combustion chamber temp high. And you want part of the intake passage way cool for air density and part of it hot for fuel vaporization. Unfortunately they are all tied together with the same metal parts so you have to compromise on everything.

“Thanks a bunch, your book has really helped me out. I’m 22 and just got my race car started for the first time on Methanol …”? From PT

After his FIRST season with mechanical fuel injection on a BLOWN GAS bracket dragster, one of our previous Fuel Injection Racing Secrets book customers wrote the following:

“This combination … can be driven to the staging lanes from the pit, shutdown, then restarted by the driver without assistance, (more…)

We made the trek to Bonneville only to find it was rained out. Luckily, while we were there we learned a few things from racers in the area.

Tip #1 To go over 420 MPH, 4 wheel drive is probably necessary to overcome the air resistance.

Tip #2 One engine builder cautioned me that he put 20% nitro in his normally aspirated race engine that previously ran on straight methanol.? He said that he made numerous jetting adjustments and no matter what combination that he tried, the racecar slowed down.? (FYI: another experienced nitro racer said that he was successful at making more power with any percentage of nitro — high or low.? As a result, we are currently researching nitro for a possible future publication to reveal the cause of differences such as this).

Tip #3 The air is thinner and easier to go fast in. This is especially for forced induction engines that can use supercharging to overcome the loss in air density to the engine.