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Old 25th May 2009, 20:05   #1
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Default Improving OHC's road dynamics at high speed

Almost all OHC owners can attest to the fact that the OHC feels scary at anything after 130-140. Now, granted that the car is very light, but then aren't F1 cars light too?

Rather than going for an outright 600 horsepower monster OHC which can't be handled properly around bends greater than 15 degrees or so, I'd love to go for mods which will make the OHC safe to drive at the speeds it can currently do. The OHC will always have understeer owing to its engine/drive configuration, but I'm looking for ways to mod the car so that it atleast gives me confidence to push it over 140.

My current VTEC is bone stock, except for 195/60 14 Goodyear GSD2s. The suspension is being overhauled as I type, but I've put the mechanic on hold until I get suggestions from you guys. So now it's you people's turn. I'm do not mind winglets at the front, or air-intakes from the front bumper which are directed upwards giving some drag and downforce. I understand that words like downforce are laughed at by most people who say that such modifications aren't really needed for moderately high speeds. But from getting a feel of the car at 130+, I'm of the opinion that some front downforce will really give the car a better feel.

So out with your suggestions people, and please don't make fun of me for using words like downforce
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Old 25th May 2009, 20:41   #2
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If you're overhauling the suspension then go in for stiffer springs, maybe lowering the car slightly. The wide tyres are a start.
Next look at getting a front strut bar to help with body flex at high speed corners. It will also help correct some understeer.

Then all I think you need is to get a broader wing than stock, if you want to play with the aerodynamics and increase the downforce a lot, then angle it upwards. Else there really is nothing else you need to do. The front bumper mod is not necessary as the engine is there, so majority of the weight is out front, i believe it's the rear which steps out of line in your case.

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Old 25th May 2009, 23:59   #3
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Quote:
Originally Posted by pranavt View Post
Almost all OHC owners can attest to the fact that the OHC feels scary at anything after 130-140. Now, granted that the car is very light, but then aren't F1 cars light too?

Rather than going for an outright 600 horsepower monster OHC which can't be handled properly around bends greater than 15 degrees or so, I'd love to go for mods which will make the OHC safe to drive at the speeds it can currently do. The OHC will always have understeer owing to its engine/drive configuration, but I'm looking for ways to mod the car so that it atleast gives me confidence to push it over 140.

My current VTEC is bone stock, except for 195/60 14 Goodyear GSD2s. The suspension is being overhauled as I type, but I've put the mechanic on hold until I get suggestions from you guys. So now it's you people's turn. I'm do not mind winglets at the front, or air-intakes from the front bumper which are directed upwards giving some drag and downforce. I understand that words like downforce are laughed at by most people who say that such modifications aren't really needed for moderately high speeds. But from getting a feel of the car at 130+, I'm of the opinion that some front downforce will really give the car a better feel.

So out with your suggestions people, and please don't make fun of me for using words like downforce
At the speeds that you have mentioned, its not aerodynamic grip aka "downforce" that you need. You need more mechanical grip- from the chassis and other components. So sort that out before you go out and get that massive multi-deck wing and front splitters.

The key components are suspension and rubber- sort that out and OHC will feel decently stable at those speeds. No need to go for fancy lowering springs and all, get your suspension re-valved by an expert, someone who knows what he his doing- a good rally/circuit tuner should be able to help you out. You need to tell him what kind of roads you drive on most, and what kinda speeds you expect the car to be stable at. Lets accept it, OHC is an aging chassis and hence has a lot of flex built unless it has done really low mileage and driven extremely carefully (no pothole bashing/impacts etc). So one needs to put in work into it to ensure that it is a joy to push around corners- and not just a straight line queen.

Hope this clears it up. One thing to remember- this revalving business is a serious affair, go to someone who knows what he is doing since redoing it is a pain and will cost you unwanted cash and headaches.

I havn't seen cars shod with the rubber you have mentioned, but I'm sure you can get better stuff. Get AD-07s if your budget allows, otherwise settle for something else. Trust me rubber transforms the character of a car, and more so at higher speeds. OHC has good brakes from the factory- if it has the rubber to use their full potential- adds a whole bunch of confidence to high-speed driving.

You can make an OHC behave extremely well on tarmac. I've been able to pull some serious Gs on a lightly tuned OHC with a suspension job and crappy Turanzas. Its a dream to handle once done right- the paltry weight already getting half the job done. Good Luck.


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Originally Posted by DocG View Post
The front bumper mod is not necessary as the engine is there, so majority of the weight is out front, i believe it's the rear which steps out of line in your case.

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Dude, its a FF family sedan. Under no circumstances whatsoever will the rear step outta line unless provoked massively (i.e. using the handbrake or a mid-corner liftoff coupled with a Scandinavian flick). It will understeer at the limit and nothing else. Having the weight in the front has nothing to do with this since the driven wheels are out front as well.

Last edited by doomsday : 26th May 2009 at 00:03. Reason: added quote...
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Old 26th May 2009, 00:19   #4
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IMO speak to guys like viper and jitu who have worked extensively on the ohc. i think getting slightly stiffer springs and better 205 rubber will make it much better.
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Old 26th May 2009, 00:33   #5
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Quote:
Originally Posted by doomsday View Post
The key components are suspension and rubber- sort that out and OHC will feel decently stable at those speeds. No need to go for fancy lowering springs and all, get your suspension re-valved by an expert, someone who knows what he his doing- a good rally/circuit tuner should be able to help you out.
Any recommendations about the same?

Quote:
Lets accept it, OHC is an aging chassis and hence has a lot of flex built unless it has done really low mileage and driven extremely carefully (no pothole bashing/impacts etc). So one needs to put in work into it to ensure that it is a joy to push around corners- and not just a straight line queen.
You think strut braces at the front and back will help?

Quote:
I havn't seen cars shod with the rubber you have mentioned, but I'm sure you can get better stuff. Get AD-07s if your budget allows, otherwise settle for something else. Trust me rubber transforms the character of a car, and more so at higher speeds. OHC has good brakes from the factory- if it has the rubber to use their full potential- adds a whole bunch of confidence to high-speed driving.
I kept overrating my tyres until today. I locked the front wheels at 120kph. Obviously this was in a controlled environment with full safety equipment, medical choppers on standby, 2 paramedics and a truckload of advanced medical equipment with 2 sets of all transplantable organs available nearby. LOL, not really.

Quote:
You can make an OHC behave extremely well on tarmac. I've been able to pull some serious Gs on a lightly tuned OHC with a suspension job and crappy Turanzas. Its a dream to handle once done right- the paltry weight already getting half the job done. Good Luck.
Can you elaborate on the suspension job?

Quote:
Dude, its a FF family sedan. Under no circumstances whatsoever will the rear step outta line unless provoked massively (i.e. using the handbrake or a mid-corner liftoff coupled with a Scandinavian flick). It will understeer at the limit and nothing else. Having the weight in the front has nothing to do with this since the driven wheels are out front as well.
Besides, why would the back step out at high speeds. Braking, alright. But if the back steps out of line at high speeds, there are much bigger problems for the car and yourself too.

Quote:
Originally Posted by DocG
If you're overhauling the suspension then go in for stiffer springs, maybe lowering the car slightly. The wide tyres are a start.
Next look at getting a front strut bar to help with body flex at high speed corners. It will also help correct some understeer.
Was already thinking of going for stiffer springs and lowering the car. But potholes and speed bumps scare me. I'm not looking for huge wings since I'm not expecting my car to break the sound barrier, just feel like the front could use some better aerodynamic mods.

Quote:
Originally Posted by akshay1234
IMO speak to guys like viper and jitu who have worked extensively on the ohc. i think getting slightly stiffer springs and better 205 rubber will make it much better.
I've heard that 205 rubber tends to foul. Will still accept opinions from people who're running the same on their OHCs. Viper seems to be banned right now, and I'd rather have the stuff out in the open since it's useful to almost all OHC owners anyways. Will wait for Jitu to post in this thread though.
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Old 26th May 2009, 00:35   #6
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nope i dont think 205 fouls. vipers had it on his car for ages. 225 works in the front but it fouls at the rear.
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Old 26th May 2009, 00:37   #7
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Will have to get the offset values and choose the correct alloys accordingly, since the inner part of my 195s on OEM alloys rubs with the wheelwell.
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Old 26th May 2009, 00:40   #8
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Quote:
Originally Posted by pranavt View Post
Will have to get the offset values and choose the correct alloys accordingly, since the inner part of my 195s on OEM alloys rubs with the wheelwell.
yup probably a slightly negative offset. just FYI viper has lenso dash and his 225 drag radials didnt seem to rub or foul at the front. he was running 205s at the back so i dunno.
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Old 26th May 2009, 01:05   #9
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Originally Posted by akshay1234 View Post
IMO speak to guys like viper and jitu who have worked extensively on the ohc. i think getting slightly stiffer springs and better 205 rubber will make it much better.
205-section rubber is an overkill on a near-stock (I assume) OHC. Its the quality of the contact patch and not the quantity of it that matters. Getting some good 195s is better than getting some crappy 205s which will increase unsprung weight and offer the same (or worse) lower grip. In an OHC, every bit of weight makes its presence felt, especially when its unsprung. And yeah, don't even think about going above 15" if you plan to use the car daily on Bombay roads.

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Originally Posted by pranavt View Post
Any recommendations about the same?
I dunno if any tuners in Bombay are into hardcore professional rallying, racing- talk to someone who is in this scene, Fahad has recently prepared a car for the circuit so he might be in on this. Also try Karan, I'm sure he is on how it would work, dunno if anyone undertakes the job though. In Blore there are a few people I know who can get this done right.

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Originally Posted by pranavt View Post
You think strut braces at the front and back will help?
Not much. Whatever off the shelf stuff you will get is bound to be useless, for a strut bar to work it needs to be designed ground up in conjunction with the suspension, taking the weakest points of the setup into account. If you aren't going rallying, you don't need it. A simple flimsy brace that ties two strut tops together is about as useful as an ejector seat on a helicopter.

Quote:
Originally Posted by pranavt View Post
I kept overrating my tyres until today. I locked the front wheels at 120kph. Obviously this was in a controlled environment with full safety equipment, medical choppers on standby, 2 paramedics and a truckload of advanced medical equipment with 2 sets of all transplantable organs available nearby. LOL, not really.
???

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Originally Posted by pranavt View Post
Can you elaborate on the suspension job?
Same thing stated in the above post, revalved dampers with different oil, resusing the stock springs (no cutting and all). The car retains the stock ride height but is much more stiff overall.

Last edited by doomsday : 26th May 2009 at 01:13.
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Old 26th May 2009, 03:58   #10
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Got stiffened stock shocks with 195/60 R14 Potenza G3s. Car performs really well on smooth as well as bumpy roads.

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Old 26th May 2009, 04:05   #11
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Quote:
Originally Posted by pranavt View Post
You think strut braces at the front and back will help?

Was already thinking of going for stiffer springs and lowering the car. But potholes and speed bumps scare me. I'm not looking for huge wings since I'm not expecting my car to break the sound barrier, just feel like the front could use some better aerodynamic mods.
Go only for a front brace. It will help the understeer. Rear braces will cause more understeer. Braces do help a lot. I've driven a lot of cars with and without them, and the decrease in chassis flex is extremely noticeable! Don't know why anyone would talk you out of it. Most ready made strut bars are specially designed and fabricated. I would however recommend a fixed brace without hinges.

With higher spring rates, ride height can be lowered without any problem. However finding the right balance between comfort and performance is key. For a bone stock ride don't go above 350F and 400R. Springs matter more than shocks here, a regular rebuild of the shocks will suffice.

Idealy increasing drag would be stupid, making it more aerodynamic is good, but not at all necessary in your case. The spoiler should also be designed properly, OE is good enough, please don't go for any of that custom fabricated crap. IF you do want a wing get one from a reputed company.

Just my 0.02
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Old 26th May 2009, 11:21   #12
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205s perform well on ohcs. get the suspension oil changed and slightly stiffened. this should make the car a bit more planted. talk to the tuners to get it done. this is a cheap and relatively good way of improving the suspension.
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Old 27th May 2009, 00:55   #13
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doomsday is giving some good advice, listen to what he says.

Of course, the rally guys have some experience with this chassis, so you may be able to find a complete off-the-shelf rally setup for a low cost.

If you don't, however, here's my "free" advice for the day, in order of where money should be spent first:

1) Tires - Improvement in behavior at all speeds.

Get the best tires you can find in 195 width and 50-60 profile in 15" dia. No need to go above that for stock power. Skinny and sticky tires will give a lot better steering feel at all speeds, plus you will approach the limit in a much more predictable way, very important on the street.

2) Shocks - Improvement in high speed road holding and controlling body movement at all speeds.

Get the best dampers you can within your budget. OTS Koni or Bilstein HD are some of the best for road-going sedans, see if something from an older civic model fits your car. Or, ask one of the rally guys like doomsday says. If I have 25k to spend on suspension, I would spend 20k on shocks and the rest on everything else. That's how important shocks are, dont let anyone tell you anything else.

There is no need for adjustable damping on any kind of road car, no matter how fancy it may be except to improve ride.

3) Anti-roll Bars - Improvement in controlling body movement and reducing body roll at the limit.

I don't know if the City uses an anti-roll bar in the back or not, but if it does, try to source a matched set front and rear from an older model civic or something.

4) Bushings - Improvement in vehicle feel through quick maneuvers and at high speeds.

Significant improvement in feel can be had with a full set of polyurethane bushings. Energy Suspension in the US and Polybush of the UK make some for Hondas. This will remove most of that sloppy feel and floatiness at high cornering loads. The tradeoff is a little harshness when you hit a rough patch. The differences are subtle, but very noticeable if you're familiar with the car.


5) Springs - In a street car, there is no control over what kind of surfaces the car will see. The stiffer the springs are, the less the grip available to the tires. Which is why, keep the stock springs, unless you want to lower the car a little. In which case, go no more than 50% stiffer than stock.

Someone said 350F, 400R which is too much for Indian conditions. It will not work very well, guaranteed.

Strut bars etc. give very little gain for too much money. Stay away unless going considerably stiffer on spring rate.

6) Alignment - This is mandatory no matter what you do to the suspension. Again, I have no clue if the City has adjustable camber or not, but some negative camber (1 to 1.2 degrees) is always good both front and rear. A slight amount of toe-out in the front (about 0.1 deg) and toe-in in the rear (0.1 to 0.2 deg) is a good starting point and will give a compromise between quick steering and high-speed stability. Caster should be maximized as much as possible.

Last edited by ananthkamath : 27th May 2009 at 00:58.
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Old 27th May 2009, 02:32   #14
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Quote:
Originally Posted by pranavt View Post
Almost all OHC owners can attest to the fact that the OHC feels scary at anything after 130-140. Now, granted that the car is very light, but then aren't F1 cars light too?

Rather than going for an outright 600 horsepower monster OHC which can't be handled properly around bends greater than 15 degrees or so, I'd love to go for mods which will make the OHC safe to drive at the speeds it can currently do. The OHC will always have understeer owing to its engine/drive configuration, but I'm looking for ways to mod the car so that it atleast gives me confidence to push it over 140.
What tires are you running and in what condition are they?
First thing you need for high speed stability (in a straight line) is stiffer shocks. Not even tires. The OHC is dampers are extemely soft and this causes floatiness at high speed. If you are going to put new shocks from the dealer anyway...then this is the best time to pay that extra 25% or whatever and go for stiffer ones. Konis are probably the most proven option.

The other stuff can come one by one unless you have the budget.

Last edited by Mpower : 27th May 2009 at 02:47.
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Old 27th May 2009, 11:35   #15
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Originally Posted by ananthkamath View Post

4) Bushings - Improvement in vehicle feel through quick maneuvers and at high speeds.

Significant improvement in feel can be had with a full set of polyurethane bushings. Energy Suspension in the US and Polybush of the UK make some for Hondas. This will remove most of that sloppy feel and floatiness at high cornering loads. The tradeoff is a little harshness when you hit a rough patch. The differences are subtle, but very noticeable if you're familiar with the car.
Have heard about PU bushings. Maybe they can be stripped and measured, and then ordered from these guys. I'm sure most of the stuff from 1987-91 and later Civics would be shared by the OHC since they share bits of suspension layout.

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Originally Posted by ananthkamath View Post

Springs - In a street car, there is no control over what kind of surfaces the car will see. The stiffer the springs are, the less the grip available to the tires. Which is why, keep the stock springs, unless you want to lower the car a little. In which case, go no more than 50% stiffer than stock.
Isn't 50% stiffer a lot, for road use? As you said, given the undulations even our best roads have, I've had some hairy experiences with stiffer springs where the car tends to take off at triple digit speeds. I don't know what kind of spring rates those lowering Eibachs come with, but I would rather stay away from all that and work with stock springs.

Quote:
Originally Posted by ananthkamath View Post

6) Alignment - This is mandatory no matter what you do to the suspension. Again, I have no clue if the City has adjustable camber or not, but some negative camber (1 to 1.2 degrees) is always good both front and rear. A slight amount of toe-out in the front (about 0.1 deg) and toe-in in the rear (0.1 to 0.2 deg) is a good starting point and will give a compromise between quick steering and high-speed stability. Caster should be maximized as much as possible.
Excellent. I missed out this bit completely. A good alignment is a must to maximise the gains from the chassis setup. And of course, elementary is the tyre pressure. Maintain correct pressures will go a long way in making your car behave- and when I say correct tyre pressures, don't go by the gauges in puncture shops and even petrol bunks, most aren't well calibrated. Find one that is, and stick to it. Otherwise get a reliable handheld gauge, its a worthy investment.

Quote:
Originally Posted by Mpower View Post

First thing you need for high speed stability (in a straight line) is stiffer shocks. Not even tires. The OHC is dampers are extemely soft and this causes floatiness at high speed. If you are going to put new shocks from the dealer anyway...then this is the best time to pay that extra 25% or whatever and go for stiffer ones. Konis are probably the most proven option.
I don't think Konis are available for the OHC. Other options are D2 and Hot-Bits. The thing is, once you upgrade the struts, without upgrading tyres- they will soon max out- especially during sudden braking at high speeds since OHC brakes are extremely effective and do not fade even under repeated torture. The stiff suspension setup makes the rubber reach its limit very quickly, under braking and to an extent- under cornering. IMO stiffened shocks and tyres+ a good alignment should work out well for starters and then you can drive around with the setup for a while and see if you can reach its limits (in a safe environment of course). That will be the time for other stuff to come in. But trust me it'll take a while to hit that plateau.
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