Lotus 7 D mod. - Page 2 - PeachParts Mercedes-Benz Forum

t walgamuth · #16 04-12-2015, 08:34 PM

Just got home before dark. The Indiana northwest region of the scca is a relatively small club with a lot of very friendly members. they run a low key event normally and among their members there are not a lot of fancy cars. Usually there are a few cars and drivers that show up from the Chicago area and south bend. Not many from the Indy region but today there were two of us there. Attendance I'd estimate has never been much over 40 drivers that I can remember.

Today there must have been an event from the Chicago region cancelled because a whole slug of hotshoes from that region showed up. 95 drivers.

I drove my new car for the first time this morning off my trailer and over to tech. So when the event started my first run was my first time to try to drive it fast. The first couple of runs I was just getting the feel of the car. not much throttle...easy into the corners and a bit harder going out. As I picked up the pace, after my third run the g forces on my brain were disorienting and I began to doubt if I could ever really drive it.

I had two more runs in which I concentrated on applying the power smoothly and driving tidily. With the power of this car though its wanting to go sideways every time you apply throttle in a turn. When you are able to give it full throttle the instantaneous response is a real rush. I can only compare it to what it must feel like getting ejected from a fighter plane. Push the throttle BLAM! (Shot out of a fighter).....drive to the next corner, get it out the other side and nearly straight.....push the gas....BLAM! (Shot out of a fighter again). Each time you punch it its like getting shot out of a fighter...BLAM!..fun!

By the third or fourth run I began to use the brakes a little on the course, enough to notice that I had way too much rear brake and not enough front. I pulled the hood and looked at the brake proportioning valves, trying to remember how to adjust them....not sure but gave it a shot. Seemed maybe better so maybe I did it correctly.

The seating position may have a lot to do with my culture shock to the driving experience of this car....sitting on the rear axle you feel every degree of drift immediately and with a real jolt of energy when it is applied.

When I went over to look at the results I found I was 20th of 95 on PAX. Beaten by an assortment of cars which perhaps should have been slower....Miatas and such. Later I found that a couple of them were blown and sporting huge wings on the rear deck, and with the hotshoes from the Chicago region, perhaps it was a decent result for an old man with a really fast new to him car.

The car ran like a stock Accura....starting up right away, idling docilly and kept its cool all day.

A really good day. (I'll sleep well tonight).

Things to do....
1. Look at brake proportioning valves.
2. Look at reducing unsprung weight.
3. Check alignment.

Joseph_Conrad · #17 04-12-2015, 09:27 PM

Glad it went well! Fun!

mytmousemalibu · #18 04-13-2015, 02:00 AM

Quote:

Originally Posted by t walgamuth

My car was built by Del Long in Iowa. It is based on a CMC chassis. It has an Accura 2 liter motor from a 2002 car. It is an engine with square bore and stroke with four valves per cylinder, and variable timing on both cams. Its been dynoed at 230 hp and about 160 torque. I believe that is wheel hp. The torque curve is virtually flat from about 2000 rpm to 9000. It is set up to run on E85. It has a rev limiter set for 9200 rpm IIRC. It has a dry sump and an alternator.

It has a four speed trans from a corolla with first and second gears removed. It is designed to be able to take off in third or fourth gear and not have to shift underway at all. The engine is offset to the right so that the ds comes through where the passenger would sit and the back of the engine is sitting on the centerline between the front and rear wheels, the max setback allowed.

The rear axle is a circle track midget style with a magnesium center section and a torsen limited slip. Its a live axle. the 7.56 quick change diff is offset to the right to line up with the engine. The brakes and front uprights are corolla, I believe.

There is a kirkey aluminum seat which is on a track and adjustable, a quick release steering wheel, a large tach, an oil pressure gauge and oil temp gauge. When down in the car my nose is a couple inches higher than the top of the valve cover and my butt is inches from the asphalt. There is room in the cockpit and footwell. Compared to the needle nosed Formula ford this will be like driving bubba's F150 to the store for a six pack and some chips. I'll be able to wear my normal street shoes while driving it.

It is built for one thing, to go fast and be lightweight. It has 13 x 10 midget wheels all around with rear tires a bit bigger than front. The weight is about 1250 and distribution is about 45/55 front to rear.

Its all prefinished yellow aluminum and pop rivets. Every body panel can be removed with dzues fasteners down to the frame. It looks brutal and all business and it is.

With two different drivers it has won five national championships and finished on the podium numerous times as well. I went looking for a race ready D mod capable of being competitive and for not a lot more money was able to buy this lovely car.

Although the builder is one of the best and cleverest around I have spotted a few places I think I can reduce the weight a little. I need to take out about 20# to stay on the minimum weight. I have to weigh at least 1450 including the driver, ready to race.

I can't wait to drive it.

That is an impressive build! Wow, i'd be excited to drive it too

97 SL320 · #19 04-13-2015, 06:12 PM

Quote:

Originally Posted by t walgamuth

By the third or fourth run I began to use the brakes a little on the course, enough to notice that I had way too much rear brake and not enough front.

Maybe not. A bit heavy on the rear brakes will allow the car to rotate when entering a corner. You could dial it towards the front then work more to the rear as you get used to the car.

Quote:

Originally Posted by t walgamuth

Things to do....
1. Look at brake proportioning valves.

Are these the actual valve in the brake line or dual master cylinders with a balance bar?

Quote:

Originally Posted by t walgamuth

2. Look at reducing unsprung weight.

Why? At this point reducing unsprung weight isn't going to give much of a gain and will be very expensive. On a smooth surface unsprung weight isn't much of an issue. Rotating weight has a side benefit of reducing unsprung weight ( wheels / hubs / rotors ) but is expensive.

Quote:

Originally Posted by t walgamuth

3. Check alignment.

Did you get any set up sheets?

For some background, I've run auto X on and off since 89 and road raced a Formula Ford in the mid 90's

t walgamuth · #20 04-13-2015, 09:14 PM

Quote:

Originally Posted by 97 SL320

Maybe not. A bit heavy on the rear brakes will allow the car to rotate when entering a corner. You could dial it towards the front then work more to the rear as you get used to the car.

Yeah, I suppose. The car seems to rotate fine though without having the rears do most of the braking.
Are these the actual valve in the brake line or dual master cylinders with a balance bar?

Actually the car has both. I used the valves yesterday because the adjusting bar was not really accessible enough and the labels saying which way to turn for front and rear were unclear.
Why? At this point reducing unsprung weight isn't going to give much of a gain and will be very expensive. On a smooth surface unsprung weight isn't much of an issue. Rotating weight has a side benefit of reducing unsprung weight ( wheels / hubs / rotors ) but is expensive.

Yeah, I know, on smooth surfaces....but how often do I run on smooth surfaces? I need to reduce weight overall because I weigh about 20 # more than Jeff and in looking at the car all the easy stuff has been done except the rotors which are solid and can be drilled or replaced with lighter ones, I think, and possibly the front uprights. Also the front fenders are presently unsprung. I am going to look and see how hard it would be to mount them to the frame instead of the upright.

Did you get any set up sheets? No. Jeff says he thinks it has 4 degrees castor. I might try to increase that. there is also some play in the steering column which I may pursue eliminating.

For some background, I've run auto X on and off since 89 and road raced a Formula Ford in the mid 90's

Well, it appears you have some experience in setting up a car then.

Mölyapina · #21 04-14-2015, 12:45 AM

Dumb question, but do you need the front fenders? What purpose do they serve?

t walgamuth · #22 04-14-2015, 06:55 AM

I am required to have fenders which cover at least 50% of the front tire as viewed from straight above. Good point though. I am going to look at the fenders which are mounted on the upright and see If its practical to mount them on the frame.

97 SL320 · #23 04-14-2015, 06:21 PM

The fenders are a rules thing, D Mod also covers full bodied production cars that must retain some semblance of a car.

The problem with frame mounted fenders is that they need to be high enough to clear the tire at full compression. This puts then pretty high where they will catch air ( drag ) and may block view. By the time you make suitable mountings, the total weight will increase.

As a test you could remove the fenders run B Mod and do an A - B - A test to see if the loss if unsprung weight helps.

t walgamuth · #24 04-14-2015, 06:59 PM

Yeah. the weight of the current mounting brackets looks pretty substantial too.

t walgamuth · #25 04-15-2015, 10:40 AM

In looking at the front of the car today, I could not find any spring action at all. The car feels as solid as a go kart. Hmmmmmmm. Apparently its fast this way.

I also looked at the play in the steering. I found a quarter inch of wear in the quick release steering wheel hub, so interchanged the spare wheel which has half as much. Most of the play remaining seems to be in the center mount rack and pinion.

I'm tentatively planning to run on Saturday and Sunday at Grissom. Saturday is a dragcross which I've never done. Its a drag strip start for about an eighth of a mile then several autocross turns. I may change the diff ratio so I can use two gears on takeoff.

t walgamuth · #26 04-17-2015, 11:01 PM

I'll be off at 7 am tomorrow or so. Sunday its supposed to rain so I may stay home.

panZZer · #27 04-18-2015, 05:24 PM

Quote:

Originally Posted by Jooseppi Luna

Dumb question, but do you need the front fenders? What purpose do they serve?

They are kinda handy in the rain, keeps the splas off ya, especially in an open rod

panZZer · #28 04-18-2015, 05:30 PM

Quote:

Originally Posted by t walgamuth

In looking at the front of the car today, I could not find any spring action at all. The car feels as solid as a go kart. Hmmmmmmm. Apparently its fast this way.

I also looked at the play in the steering. I found a quarter inch of wear in the quick release steering wheel hub, so interchanged the spare wheel which has half as much. Most of the play remaining seems to be in the center mount rack and pinion.

I'm tentatively planning to run on Saturday and Sunday at Grissom. Saturday is a dragcross which I've never done. Its a drag strip start for about an eighth of a mile then several autocross turns. I may change the diff ratio so I can use two gears on takeoff.

Ok ill say, you have sorta come to your senses , (as far as the leprecon car you were considering). This is more cooler,
I do not approve of the japanese engine. yank it out and install the 195-starting--ecotech ~ with a snail bolted to the exhaust flange, and programmable--maybe with one o them "smart" phones (finnaly come up with an actual usefull use

)

It spurs me back into another project i got going-- yet- Damn, the bigger one takes precedence.... (its like what hauls the toys to the track).

t walgamuth · #29 04-18-2015, 09:37 PM

I understand that the ecotech weighs 50
# less. But the conversion would cost what, 4 to 5000? Ehhhhh, no friggin way! This acura engine is a great engine! Only way I'd consider changing it is if it blows up or something.

I had a great time taking off from a standing start. It is pretty amazing that I can take off from a dead stop and lay two stripes about 100 feet or more. I am getting more comfortable with the car. Driving means steering with the rear end. It feels something like driving a power boat!

It is truly amazing! I got so far sideways today a couple of times I was not at all certain I'd keep it going without spinning out, but I did.

I qualified in the fastest of six groups. Beat my first matchup with a F mod car which should have been able to beat me but he spun it out, then got eliminated by the three time B mod national champ in his champ winning car....a car which is faster than mine and a driver as well.

You run twice, once in the left lane and once in the right. I had such a good run in the right lane that I actually thought I had a chance to beat him, then tried a little too hard in the other lane and overdrove a couple of corners.

interesting setup.

t walgamuth · #30 04-19-2015, 06:31 AM

The handling is so much more forgiving than the FF was. There is a massive amount of mechanical grip and the car will tolerate being slid more than anything I have driven. I was so far gone a couple of times yesterday and able to bring it back in line. the brake balance also felt very good. I found I can even brake a bit while turning and get away with it.

The car gives off this indestructible vibe.....it feels like an anvil. The motor is just gorgeous....it starts up in an instant and just sits there idling like a totally stock street engine.....but squeeze the throttle and the power comes on like Niagara falls!

The car has a set of old Hoosiers which cannot really have much grip left. I can imagine it will go a lot better with a new set of Hoosiers.

Yep......having fun!